libffi Darwin support

[David Edelsohn]

>>>>> Bryce McKinlay writes:

Bryce> It ought to be possible to get around any such issues with some 
Bryce> preprocessor macros in the assembly. Assuming that doesn't get too ugly,
Bryce> it would definatly be nice to merge them.

	It would be nice to merge the assembly language using some of the
macros from gcc/ginclude/ppc-asm.h.  I am more interested in ffi_darwin.c,
to begin with, because that really *is* identical.

David