copyright: update the years, use ranges, and explain this usage

The interval 2013-2017 for the Free Software Foundation is valid
because in those years there were releases with changes by either
Chris or David, and the GNU maintainers guide advises to mention
a new year in all files of a package, not just in the ones that
actually changed, and be done with it for the rest of the year.

README

@@ -65,5 +65,12 @@ Bug Reports
 
 Current Status
 
-	GNU nano has reached its seventh milestone, 2.6.x.  Since 2.5.0, it
-	is a "rolling" release: bug fixing and development go hand in hand.
+	Since version 2.5.0, GNU nano has abandoned the distinction between
+	a stable and a development branch: it is now on a "rolling" release
+	-- fixing bugs and adding new features go hand in hand.
+
+Copyright Years
+
+	When in any file of this package a copyright notice mentions a
+	year range (such as 1999-2011), it is a shorthand for a list of
+	all the years in that interval.

configure.ac

 # Configuration for GNU nano - a small and user-friendly text editor
 #
-# Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
-# 2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.
+# Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.
+# Copyright (C) 2014, 2017 Mike Frysinger
 #
 # GNU nano is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published

doc/nano.1

-.\" Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
-.\" 2009, 2010, 2013, 2014 Free Software Foundation, Inc.
+.\" Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.
 .\"
 .\" This document is dual-licensed.  You may distribute and/or modify it
 .\" under the terms of either of the following licenses:

doc/nano.texi

@@ -30,8 +30,7 @@ This manual documents GNU @code{nano}, a small and friendly text editor.
 
 This manual is part of the GNU @code{nano} distribution.@*
 @sp 4
-Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
-2009, 2014, 2015 Free Software Foundation, Inc.
+Copyright (C) 1999-2009, 2014-2017 Free Software Foundation, Inc.
 
 This document is dual-licensed.  You may distribute and/or modify it
 under the terms of either of the following licenses:

doc/nanorc.5

-.\" Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011,
-.\" 2013, 2014, 2015 Free Software Foundation, Inc.
+.\" Copyright (C) 2003-2011, 2013-2017 Free Software Foundation, Inc.
 .\"
 .\" This document is dual-licensed.  You may distribute and/or modify it
 .\" under the terms of either of the following licenses:

src/browser.c

 /**************************************************************************
  *   browser.c  --  This file is part of GNU nano.                        *
  *                                                                        *
- *   Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,  *
- *   2010, 2011, 2013, 2014, 2015 Free Software Foundation, Inc.          *
+ *   Copyright (C) 2001-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2015, 2016 Benno Schulenberg                           *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/chars.c

 /**************************************************************************
  *   chars.c  --  This file is part of GNU nano.                          *
  *                                                                        *
- *   Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,  *
- *   2010, 2011, 2013, 2014 Free Software Foundation, Inc.                *
+ *   Copyright (C) 2001-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2016 Benno Schulenberg                                 *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/color.c

 /**************************************************************************
  *   color.c  --  This file is part of GNU nano.                          *
  *                                                                        *
- *   Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,  *
- *   2010, 2011, 2013, 2014, 2015 Free Software Foundation, Inc.          *
+ *   Copyright (C) 2001-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2014, 2015, 2016, 2017 Benno Schulenberg               *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/cut.c

 /**************************************************************************
  *   cut.c  --  This file is part of GNU nano.                            *
  *                                                                        *
- *   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,  *
- *   2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.    *
+ *   Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2014 Mark Majeres                                      *
  *   Copyright (C) 2016 Benno Schulenberg                                 *
  *                                                                        *

src/files.c

 /**************************************************************************
  *   files.c  --  This file is part of GNU nano.                          *
  *                                                                        *
- *   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,  *
- *   2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.    *
+ *   Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2015, 2016 Benno Schulenberg                           *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/global.c

 /**************************************************************************
  *   global.c  --  This file is part of GNU nano.                         *
  *                                                                        *
- *   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,  *
- *   2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.    *
+ *   Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2014, 2015, 2016 Benno Schulenberg                     *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/help.c

 /**************************************************************************
  *   help.c  --  This file is part of GNU nano.                           *
  *                                                                        *
- *   Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,  *
- *   2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.          *
+ *   Copyright (C) 2000-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2014, 2015, 2016 Benno Schulenberg                     *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/move.c

 /**************************************************************************
  *   move.c  --  This file is part of GNU nano.                           *
  *                                                                        *
- *   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,  *
- *   2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.    *
+ *   Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2014, 2015, 2016 Benno Schulenberg                     *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/nano.c

 /**************************************************************************
  *   nano.c  --  This file is part of GNU nano.                           *
  *                                                                        *
- *   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,  *
- *   2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.    *
+ *   Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2014, 2015, 2016 Benno Schulenberg                     *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/nano.h

 /**************************************************************************
  *   nano.h  --  This file is part of GNU nano.                           *
  *                                                                        *
- *   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,  *
- *   2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.    *
+ *   Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2014, 2015, 2016 Benno Schulenberg                     *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/prompt.c

 /**************************************************************************
  *   prompt.c  --  This file is part of GNU nano.                         *
  *                                                                        *
- *   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,  *
- *   2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.    *
+ *   Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2016 Benno Schulenberg                                 *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/proto.h

 /**************************************************************************
  *   proto.h  --  This file is part of GNU nano.                          *
  *                                                                        *
- *   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,  *
- *   2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.    *
+ *   Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.    *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *
  *   it under the terms of the GNU General Public License as published    *

src/rcfile.c

 /**************************************************************************
  *   rcfile.c  --  This file is part of GNU nano.                         *
  *                                                                        *
- *   Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,  *
- *   2010, 2011, 2013, 2014 Free Software Foundation, Inc.                *
+ *   Copyright (C) 2001-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2014 Mike Frysinger                                    *
  *   Copyright (C) 2014, 2015, 2016 Benno Schulenberg                     *
  *                                                                        *

src/search.c

 /**************************************************************************
  *   search.c  --  This file is part of GNU nano.                         *
  *                                                                        *
- *   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,  *
- *   2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.    *
+ *   Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2015, 2016, 2017 Benno Schulenberg                     *
  *                                                                        *
  *   GNU nano is free software: you can redistribute it and/or modify     *

src/text.c

 /**************************************************************************
  *   text.c  --  This file is part of GNU nano.                           *
  *                                                                        *
- *   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,  *
- *   2008, 2009, 2010, 2011, 2013, 2014 Free Software Foundation, Inc.    *
+ *   Copyright (C) 1999-2011, 2013-2017 Free Software Foundation, Inc.    *
  *   Copyright (C) 2014, 2015 Mark Majeres                                *
  *   Copyright (C) 2016 Mike Scalora                                      *
  *   Copyright (C) 2015, 2016 Benno Schulenberg                           *