bump version numbers and add a news item for the 2.7.3 release

NEWS

+2016.12.28 - GNU nano 2.7.3 "Ontbijtkoek" wipes away a handful of bugs:
+		your editor is now able to handle filenames that contain
+		newlines, avoids a brief flash of color when switching
+		between buffers that are governed by different syntaxes,
+		makes the Shift+Ctrl+Arrow keys select text again on a
+		Linux console, is more resistant against malformations
+		in the positionlog file, and does not crash when ^C is
+		typed on systems where it produces the code KEY_CANCEL.
+		Oh, and it no longer mistakenly warns about editing an
+		unlocked file just after saving a new one.  That's it.
+		Tastes great with thick butter.
+
 2016.12.12 - GNU nano 2.7.2 "Shemesh! Shemesh!" brings another feature:
 		the ability to complete with one keystroke (^] by default)
 		a fragment of a word to a full word existing elsewhere in

configure.ac

@@ -16,7 +16,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see http://www.gnu.org/licenses/.
 
-AC_INIT([GNU nano], [2.7.2], [nano-devel@gnu.org], [nano])
+AC_INIT([GNU nano], [2.7.3], [nano-devel@gnu.org], [nano])
 AC_CONFIG_SRCDIR([src/nano.c])
 AC_CANONICAL_HOST
 AM_INIT_AUTOMAKE

doc/man/nano.1

@@ -17,7 +17,7 @@
 .\"   Documentation License along with this program.  If not, see
 .\"   <http://www.gnu.org/licenses/>.
 .\"
-.TH NANO 1 "version 2.7.2" "December 2016"
+.TH NANO 1 "version 2.7.3" "December 2016"
 .\" Please adjust this date whenever revising the manpage.
 
 .SH NAME

doc/man/nanorc.5

@@ -17,7 +17,7 @@
 .\"   Documentation License along with this program.  If not, see
 .\"   <http://www.gnu.org/licenses/>.
 .\"
-.TH NANORC 5 "version 2.7.2" "December 2016"
+.TH NANORC 5 "version 2.7.3" "December 2016"
 .\" Please adjust this date whenever revising the manpage.
 
 .SH NAME

doc/man/rnano.1

@@ -16,7 +16,7 @@
 .\"   Documentation License along with this program.  If not, see
 .\"   <http://www.gnu.org/licenses/>.
 .\"
-.TH RNANO 1 "version 2.7.2" "December 2016"
+.TH RNANO 1 "version 2.7.3" "December 2016"
 .\" Please adjust this date whenever revising the manpage.
 
 .SH NAME

doc/texinfo/nano.texi

@@ -6,7 +6,7 @@
 
 @smallbook
 @set EDITION 0.4
-@set VERSION 2.7.2
+@set VERSION 2.7.3
 @set UPDATED December 2016
 
 @dircategory Editors
@@ -21,7 +21,7 @@
 @titlepage
 @title GNU @code{nano}
 @subtitle a small and friendly text editor.
-@subtitle version 2.7.2
+@subtitle version 2.7.3
 
 @author Chris Allegretta
 @page