Many gnulib files contain an Emacs-specific feature like the
following, eg in build-aux/gitlog-to-changelog:
eval: (add-hook 'write-file-hooks 'time-stamp)
write-file-hooks is obsolete since Emacs 22.1 (released June 2007),
and hopefully can be removed from Emacs one day.
Please replace "write-file-hooks" with "before-save-hook".
(The literal replacement for "write-file-hooks" is "write-file-functions",
but for adding a time-stamp like you do above, "before-save-hook" is
recommended. Both replacements exist since Emacs 22.1.)