This patch will add a physics constraints replication for group instances
(dupli group).
It also fix crashing when when a group instance is made from a linked
group instance and both are on the active layer.
Initial patch T31443 from moerdn (Martin Sell).
Reviewers: lordloki, sergof, moguri, sybren
Reviewed By: moguri, sybren
Differential Revision: https://developer.blender.org/D658
0b4a71b072