Blender Git Loki

Cycles: Added feature overrides

This adds some extra options to disable certain rendering features, such as image maps, lights, shadows,
atmosphere, bump maps, etc. Intended to be used for diagnosing rendering problems.
"Inspired" by Arnold.

Cycles: Disabled anisotropic texture cache lookups for emission shaders.

Leaving it enabled lead to excessive render times in certain scenes.

Cycles: Mip map creation now respects texture extension settings

Merge branch 'master' of git.blender.org:blender into cycles_texture_cache

Merge remote-tracking branch 'origin/master' into cycles_texture_cache

Merge branch 'master' into cycles_texture_cache

Merge branch 'master' of git.blender.org:blender into cycles_texture_cache

Cycles: Added option for custom texture cache path.

Cycles: Texture Cache toggle is now properly updated.

Cycles: Fixed OpenCL kernel build on Windows.

Cycles: Fixed build on Linux and OpenCL.

Cycles: Fixed texture caching when using the new displacement nodes.

Merge branch 'cycles_texture_cache' of git.blender.org:blender into cycles_texture_cache

Cycles: Implmemented texture filtering for box mapping.

Cycles: Improved ray differentials for volume scattering.

Cycles: Fixes for OSL with texture caching: Textures are now right side up again and textures read from the cache are assumed to be linear.

Cycles: Set proper defaults for texture caching.

Cycles: Setting dNdx/dNdy to zero for flat shaded surfaces.

Cycles: Fixed uninitialised variable.

Cycles: Fixed swapped parameters in fresnel_dielectric().