Blender Git Loki

Followup for previous PBVH commit

Didn't realize the index buffer is stored once in a BVH
and same pointer is reused. Surprisingly, simple files
were fixed with the previous fix.

Now disabled the optimization all together, and it was
simpler to just completely remove all residue of the
code. It is likely to be a different implementation
anyway, so no need to try to keep code in a semi-broken
state.