Blender Git Loki

Cycles / Hair: Some cleanup and optimizations for hair code.

* Remove dead code from line segments BVH refine.
CURVE_KN_TANGENTGNORMAL and CURVE_KN_TRUETANGENTGNORMAL are either both true, or both false. Therefore a true/false condition is impossible.
This was a leftover of CURVE_CUSTOM, which was removed in r59234.

* Use "else if" in blender_curves.cpp.