Blender Git Loki

New resolve_tri_uv_v3 util function

Compute barycentric coordinates (u, v) for a point with respect to a
triangle.

This is needed for Cycles baking but we decided to push this
independently of the upcoming main baking changes.

Code adapted from Christer Ericson's Real-Time Collision Detection.

Cleanup, refactoring and review from Campbell Barton.