Blender Git Loki

Fix for bug [#31613] Cycles 3d viewport material display mode + skin modifier related crash

When in material display mode, mesh_calc_modifiers() calculates the
orco DerivedMesh, which uses a different CustomDataMask. In
particular, it does not necessarily include the current modifier's
requiredDataMask, so those layers might get set to NO_COPY. For the
skin modifier, this resulted in a crash when the modifier internally
copies the DerivedMesh and the output does not contain the expected
MVertSkin layer.

Fixed by adding the requiredDataMask to the orco DM's CustomDataMask.

Also added a debugging function to customdata.c:
customData_mask_layers__print(CustomDataMask mask);

This will print out the names of all the CD layer types in the mask.