Two modifications:
1. The addition of 2013 to the copyright year range for every file;
2. The use of a single year range, instead of potentially multiple
year ranges, as approved by the FSF.
(gdb_compile): If target is *-*-cygwin* or *-*-mingw*, and we're
compiling an executable, link in an object that forces unbuffered
output.
* lib/set_unbuffered_mode.c: New file.
