Fix Cycles Windows render errors with BVH2 CPU rendering
Fix Cycles Windows render errors with BVH2 CPU rendering

One problem is that it was always using __mm_blendv_ps emulation even if the
instruction was supported. The other that the emulation function was wrong.

Thanks a lot to Ray Molenkamp for tracking this one down.

tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird