Import simpler crypto/md5 module from gnulib, plus stdint module.

Import simpler crypto/md5 module from gnulib, plus stdint module.

* aclocal.m4, configure, lib/Makefile.in, lib/gnulib.mk, m4/gl-comp.m4:
* src/config.in: Regenerate.
* lib/md5.c, lib/md5.h: Regenerate with simpler version, which
assumes C99-style <stdint.h>, supplied by the stdint module.
* lib/stdint.in.h, m4/longlong.m4, m4/stdint.m4: New files,
generated from gnulib.
* src/deps.mk (fns.o): Do not depend on md5.h, fixing a typo in
the earlier patch.