Blender Git Loki

Cycles: Fix wrong shading when some mesh triangle has non-finite coordinate

This is fully unpredictable for artists when one damaged object makes the whole
scene to render incorrectly. This involves two main changes:

- It is not enough to check triangle bounds to be valid when building BVH.
This is because triangle might have some finite vertices and some non-finite.

- We shouldn't add non-finite triangle area to the overall area for MIS.