Using Proxy Armature on groups: an Undo now doesn't force a complete re-evalution
of this system anymore, so posing works similar as for regular (non linked)
armatures - an undo step goes back to the previous pose.
Before, an undo made the entire armature go to rest pose. Bad bad :)
I need animators to carefully check - report back if there's other issues!
Tested on Gilga character from Tube Open Movie.
6e990de9b0