Blender Git Loki

OpenSubdiv: Changes in C-API

- Made OpenSubdiv_GLMesh private
Previously, it was still accessible via C-API from C++ code.

- Don't implicitly refine evaluator when updating coarse positions,
now there is an explicit call to do this.

Allows to first apply all changes to the coarse mesh and then
refine once.

- Added coarse positions update from a continuous buffer with given
starts offset and stride.

Allows to update coarse positions directly from MVert array.

- Refiner is no longer freed when CPU evaluator is created.
Allows to re-use refiner for multiple purposes.