Cycles: mix hair minimum width code with SSE intersection code
Cycles: mix hair minimum width code with SSE intersection code

Gives 6.5% speedup for hair.blend from testsuite.

This commit was previously reverted, but should work ok now. Patch by Sv. Lockal.

pyrochlore/cycles,tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird,pyrochlore/cycles,pyrochlore/cycles,tangent-opensource/coreBlackbird