Blender Git Loki

Cycles: Use faster ray-quad-intersection test

The original quad intersection test works by just testing against the two triangles that define the quad.
However, in this case it's actually faster to use the same test that's also used for portals: Determining
the distance to the plane in which the quad lies, calculating the hitpoint and checking whether it's in the
quad by projecting onto the sides.

Reviewers: brecht, sergey, dingto

Reviewed By: dingto

Differential Revision: https://developer.blender.org/D2045