We need to increase GPU memory usage a bit. Unfortunately we can't get away
with writing either reflection or transmission passes because these BSDFs may
scatter in either direction but still must be in a fixed reflection or
transmission category to match up with the color passes.
We need to store the continuation probability used to make the termination
decision in intersect_closest, instead of recomputing it in shade_surface.
Because otherwise a shade_volume in between can change the throughput and
change the probability.
Remove prefix of filenames that is the same as the folder name. This used
to help when #includes were using individual files, but now they are always
relative to the cycles root directory and so the prefixes are redundant.
For patches and branches, git merge and rebase should be able to detect the
renames and move over code to the right file.
