Blender Git Loki

undoexp: Tag renamed ID undo steps as 'full barrier'.

I.E. re-using data from old bmain is forbidden around an ID renaming.

This is a bit over-protective in most cases, since renaming an ID does
change its memfile data. So renamed ID should be reloaded from memfile
anyway.

But the problems might come (in some specific scenarii involving 'name
switching' between two IDs) from name-based lookup. Those could lead to
remapping some ID pointers in unchanged data-blocks to the wrong ID...