[RESEND PATCH 0/8] R600/SI Global Atomics

[Aaron Watry]

This is a resend of a series from earlier today that didn't make
it through intact due to what I believe was a mistake on my part.

Patches 1, 4, and 5 already have reviews, the others haven't been
seen on the llvm-commits list yet.

This adds in all of the 2-argument integer global atomic instructions
that were missing for OpenCL 1.2 support on SI. 

Note the 2-arg qualifier. I haven't done cmpxchg yet because that
one will be a bit more complex than these fairly mechanical
additions (due to the extra operand).