This changes the shadow record-all any-hit program to accept all
hits (return without calling optixIgnoreIntersection) beyond
the furthest distance recorded after the maximum number of hits
that can be recorded was reached.
OptiX will not call the any-hit program anymore for hits beyond
the distance of the accepted hits and also reduces the current
ray length behind the scenes. As a result performance improves
drastically in scenes where shadow rays can hit a lot of
transparent objects, like the "koro" benchmark scene.

With this applied I now get similar performance with both CUDA
and OptiX in "koro". Not quite perfect yet, but much better than
before.