DTrace/PowerPC

[Justin Hibbits]

This morning I committed the final major piece of DTrace for PowerPC, the
fasttrap (user trapping) module.  I haven't fully tested it, in fact I've
barely tested it beyond build and logic analysis, and confirming it doesn't
break anything.  I've set a MFC to a month from now, so more testing can be
done.

Anyone who has a spare machine, please please please test.  Not just
Fasttrap, but FBT and the rest, and let me know the results.

- Justin