[MLton] power pc "port"

[Stephen Weeks]

> In other programs I've used the GCC options -fno-strict-aliasing,
> which allow me to do "evil" things with pointers like the ones you
> point out at any optimization level.

Ahh yes.  Thanks.  We use -fno-strict-aliasing for the C code that
MLton generates, but not for the runtime.  I tried it out (with -O2)
with the real.sml regression and all worked fine.  This seems to be a
better solution than hoping that -O1 doesn't do something bad.  So,
I've checked it in.