Blender Git Loki

Cycles: Fix crashes after recent optimization commits

There is some precision issues for big magnitude coordinates which started
to give weird behavior of release builds. Some weird memory usage in BVH
which is tricky to nail down because only happens in release builds and GDB
reports all variables as optimized out when trying to use RelWithDebInfo.

There are two things in this commit:

- Attempt to make vectorized code closer to original one, hoping that it'll
eliminate precision issue.
This seems to work for transform_point().
- Similar trick did not work for transform_direction() even tho absolute
error here is much smaller. For now disabled that function, need a more
careful look here.