Blender Git Loki

Half Floats: Initial support for CUDA.

This is not working yet, due to an error on rendertime, I assume it's an error on reading the texture. If I render a scene, with the half float texture outside of the camera, it works.

* Enable half floats for Kepler cards (1024 for half and 1024 for half4)
* Use proper half data type for CUDA, don't declare our own.
* Change __float2half_rn to __float2half, which should be the same according to http://stackoverflow.com/questions/35198856/half-precision-difference-between-float2half-vs-float2half-rn