Blender Git Loki

* Prototyped a faster smooth algo, currently disabled.
* Wrote a new API for wrangling temporary customdata layers across pbvh types:
- SCULPT_temp_customlayer_ensure: makes sure a (named) customdata
layer exists. Works for multires; since these are temporary
layers we can safely allocate them in a temporary CustomData
structure (in ss->temp_vdata).
- SCULPT_temp_customlayer_get: initializes a special structure,
SculptCustomLayer, that is used to get per elem customdata.
- SCULPT_temp_cdata_get: Uses a SculptCustomLayer ref along with
a SculptVertexRef to look up the data.