Blender Git Loki

== PBVH ==

OK, after that failure of committing a bunch of old junk, hopefully
this is what I actually meant to commit :)

* Added big comments to some of the fields in struct PBVHNode. I
always forget the details of these, so finally wrote it down
properly.

* Changed types of PBVHNode.face_vert_indices and PBVHNode.flag to
better reflect their contents.

* There should be no functional changes here.