gmp: Don't build as Universal Binary on Snow Leopard (do i386 only).
Compile with --with-pic to avoid errors like:

(./guile-snarf-docs -DHAVE_CONFIG_H -I.. -I.. -I.. -I/usr/local/include async.c | \
		    ./guile_filter_doc_snarfage --filter-snarfage) > async.doc || { rm async.doc; false; }
ld: illegal text-relocation to ___gmp_binvert_limb_table in /usr/local/lib/libgmp.a(mp_minv_tab.o) from ___gmpn_divexact_1 in /usr/local/lib/libgmp.a(dive_1.o) for architecture x86_64

See https://github.com/mxcl/homebrew/issues/12946
Protect buildclean from failure.
libtool: Rebuild.
guile: Rebuild with GMP 5.1.1
Merge branch 'master' of github.com:rudix-mac/rudix

Conflicts:
	Ports/gmp/Makefile