Blender Git Loki

Cycles: Initial implementation of QBVH traversal for unaligned nodes

Implements both QBVH packing and traversal on SSE2+ processors.

With a test render scene render time goes from 93sec (in master) down
to 55sec. Kind of impressive, let's hope it's not because some bug and
that we can keep such a nice speedup.

Also finished some non-SIMD binary BVH code. On a test scene got about
20% of speedup comparing to 2.77a.

Well, let's verify everything, finish some remaining TODOs and make
the branch ready for master.