* make-docfile.c (write_globals): Make it a bit clearer.

This pacifies GCC 4.7.2 when Emacs is configured with
--enable-link-time-optimization and --enable-gcc-warnings.
* src/alloc.c (free_save_value): Now static.
* lisp/gnus/smiley.el (smiley-style): Make the file loadable in batch mode.
Not likely to be very useful, of course, but helps with automated testing.
* configure.ac: Document that --enable-gcc-warnings emits errors.