Blender Git Loki

Add inlined custom lnors consistency check/fixup code in BMesh version of `loops_calc_normals`

Note that stashing all clnor computations in a single func might not be optimal,
but it allows to reduce compute overhead as much as possible (it's a desing decision
in the end).

Also, looks like func used to create smooth fans from a set of custom lnors is not working
100% correct - new checking code did found some diff in lnors of same smooth fans... :/