Blender Git Loki

OpenSubdiv: Only store edges topology for non-smooth edges

This change makes it so vertices of edge are only stored when edge
has non-zero crease. This allows to lower memory footprint of 1.5M
faces from 78 MiB to 54 MiB in the case all creases are zero.

Meshes with crease are more hard to predict due to array-based
storage, so it all depends on index of edge with crease. Worst case
(all edges are creased) still stays at 78 MiB.