Be careful about ray coordinate system orientation in Curve::Intersect().
Be careful about ray coordinate system orientation in Curve::Intersect().

Aligning it with the curve gives us tighter bounding boxes and lets us exit
out of recursiveIntersect() sooner. ~12% speedup for hair-curl test scene.

nispaur/pbrt-v3,shihchinw/pbrt-v3,nyue/pbrt-v3,nispaur/pbrt-v3,shihchinw/pbrt-v3,mmp/pbrt-v3,nyue/pbrt-v3,mmp/pbrt-v3,mmp/pbrt-v3,nyue/pbrt-v3,nyue/pbrt-v3,nispaur/pbrt-v3,shihchinw/pbrt-v3,shihchinw/pbrt-v3,mmp/pbrt-v3,nispaur/pbrt-v3