[MLton] MLton on intel mac

[Florian Weimer]

* Matthew Fluet:

>> The changes I made will also align all C calls on x86 to 16 byte
>> bounds.  I don't know enough about the frame layout within SML code
>> to try this, but it doesn't seem to be necessary.
>
> It should be fairly easy to set things up to only do alignment to 16
> byte boundaries on the MacOS.

Technically, it's needed on other systems as well.  I believe
GNU/Linux adopted a modified psABI which requires 16-byte alignment as
well.  It's less apparent on these platforms because there is little
SSE library code.