* Multithreaded image loading, each thread can load a separate image.
* Better multithreading for multiple instanced meshes, different threads can now
build BVH's for different meshes, rather than all cooperating on the same mesh.
Especially noticeable for dynamic BVH building for the viewport, gave about
2x faster build on 8 core in fairly complex scene with many objects.
* The main thread waiting for worker threads can now also work itself, so
(num_cores + 1) threads will be working, this supposedly gives better
performance on some operating systems, but did not measure performance for
this very detailed yet.
and 5 float image textures. For CPU render this limit will be lifted later
on with image cache support. Patch by Mike Farnsworth.
Also changed color space option in image/environment texture node, to show
options Color and Non-Color Data, instead of sRGB and Linear, this is more
descriptive, and it was not really correct to equate Non-Color Data with
Linear.
