Blender Git Loki

Fix T50876: Cycles Crash - Cycles crashes before sampling when certain meshes have autosmooth enabled.

The root of the issue was in custom normal code, so far it assumed that
we could only have one cyclic smooth fan around each vertex, which is...
blatantly wrong (again, the two cones sharing same vertex tip e.g.).

This required a rather deep change in how smooth fans/clnor spaces are processed,
took me some time to find a 'good' solution.

Note that new code is slightly slower than previous one (maybe about 5%),
not much to be done here, am afraid.

Tested against all older report files I could find, seems OK.