document a renamed variable

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@2506 35c25a1d-7b9e-4130-9fde-d3aeb78583b8

ChangeLog

@@ -35,6 +35,8 @@ CVS code -
 	- Move the "Refresh" and "Exit" shortcuts to the beginning of
 	  the help browser shortcut list, for consistency. (DLR)
 - nano.c:
+  copy_filestruct()
+	- Rename variable prev to copy to avoid confusion. (DLR)
   print1opt_full()
 	- If desc should be empty, allow it to be NULL instead of
 	  "", since the latter is not necessarily translated as "".