Blender Git Loki

Add initial Ptex support to texture paint mode

Update Blend file saving/loading for Ptex

Add support for GPU drawing of Ptex textures to image node

RNA updates for Ptex

Add loading of Ptex UVs and layer data in Cycles

Add new CustomData layers for Ptex

Add Ptex infrastructure to GPU module

- Function to upload the Ptex face mapping data texture

- Add Ptex to GPUNodeLink

- Pass in object when binding material, used to get at Ptex layer data

- Add Ptex utility functions to the GLSL shader

Add API for packing Ptex faces into a single large image

TODO: this is much smaller now than before, can probably be moved to
better spot

Add basic Ptex reading via OIIO to ImBuf

Add Ptex shader node

Move Cycles' Ptex attribute from vertices to corners

Update DerivedMesh for Ptex drawing/rendering

- Temporary change to customdata mask

- Add ptex vertex attrib to DerivedMesh for GPU drawing

- Automatically add subsurf modifier if needed to get correct
tesselation pattern

Tesselation for Ptex loop layer