Blender Git Loki

OpenSubdiv: Optimize faces storage in mesh topology

Avoid per-face pointer and allocation: store everything as continuous
arrays.

Memory footprint for 1.5M faces:

- Theoretical worst case (all vertices and edges have crease) memory
goes down from 114 MiB to 96 MiB (15% improvement).

This case is not currently achievable since Blender does not expose
vertex crease yet.

- Current real life worst case (all edges have crease) memory goes
down from 108 MiB to 90 MiB (17% improvement).

- Best case (no creases at all) memory goes down from 96 MiB to 78 MiB
(19% improvement).