[MLton] PowerPC .deb built

[Stephen Weeks]

> It turns out that the remaining problems I had were a kernel bug.
> For hppa+profiling, one needs kernel >= 2.6.3.
> 
> I've attached my final version of the patch.

Committed, with minor tweaks.  I'm fine with using char instead of int
for _start and etext, since you've observed it to work in practice.

> I've also attached the results of profiling for the 4 platforms I tested.
> These results come after a full-rebuild of MLton.

>From a quick scan these look OK.