Blender Git Loki

Cycles: Better quality filtering for .tx mip maps

Cycles: Use texture cache only for CPU devices

Cycles: resetting texture cache stats after use

Cycles: made OSL shading use .tx files where available, added a mutex to the kernel texture name array

Cycles: a handful of fixes for texture caching

Cycles: first additions for OIIO texture caching

* TextureSystem options are exposed in the UI
* Automatic generation of .tx files is optional
* Texture lookups do not use differentials or mip maps yet, so performance is pretty bad