Blender Git Loki

Cycles: Speed up split kernel builds by using split direct_emission functions

This removes the indirect call to `svm_eval_nodes` from the
`kernel_direct_lighting` kernel, and speeds up kernel build times
by 4-5 seconds. Render time is slower by ~1%. It should be possible
to apply this technique to other areas of the kernel to get even
better build times.

Note: this breaks branched path and shadow catcher in the split
kernel. Should be an easy fix, will do later.