Blender Git Loki

Fix T54544: "Copy Materials to Selected" only works when materials are defined on the mesh.

Build a temp matarray storing materials from obdata and source object
(depending on slots 'allocation' of source object), and assign those to
targets.

Also remove limitation of 'using same obdata is forbidden', just never
edit obdata materials in that case...

Certainly not perfect, but already much better than existing code.