The driver code was almost there, but didn't work because ID nodes
have no outlinks - and using links won't be safe anyway because of
ordering issues. Instead, just loop over all IDNodes.
Animation is fixed simply by referring to ARMATURE_EVAL instead of
BONE in construct_node_identifier - the bArmature ID doesn't have
BONE components in any case, so the old identifier can't work.
a57fec986d