return NULL for malloc(0) or realloc(p, 0). (This should be done
differently than wasting one byte, but alas...)
* Moved "add'l libraries" option in Makefile to an earlier place.
* Remove argument compatibility hacks (b) and (c).
* Add grey2mono, dither2mono and mono2grey to imageop.
* Dup the fd in socket.fromfd().
* Added new modules mpz, md5 (by JH, requiring GNU MP 1.2). Affects
Makefile and config.c.
* socketmodule.c: added socket.fromfd(fd, family, type, [proto]),
converted socket() to use of getargs().
