Blender Git Loki

Code cleanups for the PBVH, no functional changes.

* Use the PBVHType consistently in pbvh_update_draw_buffers().

* Split the raycast function up, mesh and grid raycast get their own
functions now.

* Replace duplicated code in BLI_pbvh_node_add_proxy() with call to
BLI_pbvh_node_num_verts().