[bug-diffutils] updated gnulib to latest in diffutils

[Paul Eggert]

I updated gnulib to the latest version, in diffutils,
to take advantage of this recent gnulib patch:

http://git.savannah.gnu.org/cgit/gnulib.git/commit/?id=72c63c089365640c7f1acd97fb72ee26932ac2b3

to work around a bug in Sun c99.