- raytracing code now uses cylinder-line intersect for strands. It used
to intersect with the screen-aligned strand quads, giving too many
misses for tracing.
Note; mirror for hair is still not well supported!
- added in Materials a choice for whether a material is Traceable for
raytracing or whether it is part of Shadow buffers. This way you can
exclude hair strands from raytracing, but still get shadowbuffers for it.