Blender Git Loki

* PBVH node join code is now enabled for dyntopo bmesh
* Fixed bug in dyntopo bmesh time limiting code

remove accidental debug return

* Fixed undo with bmesh dyntopo

* Migrated optimizations from trimesh to bmesh dyntopo:
- Original coordinate/normals are now stored in customdata layers,
instead of being looked up in the BMLog
- Vertex "indices" are now actually pointers to BMVerts.
- Dyntopo split/collapse is now time-limited
- Increased pbvh->leaf_limit to 2000
- Nodes are split after topolgy updates, not just after the user lets up
the mouse.

* Also, renamed TMElemSet to TableGSet

TODO:
- Migrate PBVHNode->bm_[unique_verts/other_verts/faces] to TableGSet.
Currently GHash is completely inlined in this branch which does almost
the same thing performance-size; inlining GHash seems beyond the scope of this
project however.

BMesh dyntopo works again, if you disable WITH_TRIMESH in BKE_pbvh.h

Rebase branch