Blender Git Loki

undoexp: Better handling of recalc flags in undo/redo case.

Main idea here is to accumulate all recalc flags used on an ID over the
whole time between two memfile savings.

Since our IDs are now almost never fully re-evaluated in depsgraph on
undo, this should give us a best 'precise' info required to update
actually changed things in the DEG update just after the undo.