Add locking entry to sample nanorc

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@4552 35c25a1d-7b9e-4130-9fde-d3aeb78583b8

doc/nanorc.sample.in

@@ -56,6 +56,11 @@
 ## Enable ~/.nano_history for saving and reading search/replace strings.
 # set historylog
 
+## Enable vim-style lock-files.  This is just to let a vim user know you
+## are editing a file [s]he is trying to edit and vice versa. There are
+## no plans to implement vim-style undo state in these files
+# set locking
+
 ## The opening and closing brackets that can be found by bracket
 ## searches.  They cannot contain blank characters.  The former set must
 ## come before the latter set, and both must be in the same order.