[MLton] Intel Mac version of MLton

[Matthew Fluet]

> Don't start just yet.  Matthew has one more commit to make, which he
> will make soon and let you know once he has done so.

I've checked in the changes to the header files that set up a 16-byte 
aligned %esp for SML to make C calls.  According to Eric, this should let 
one bootstrap on a Darwin platform.  As I understand it, he used the 
PowerPC emulation on x86-darwin to bootstrap.  That might be somewhat 
simpler than the cross compilation.

Sources can be checked out according to the instructions at:
   http://www.mlton.org/Sources