Blender Git Loki

This one is a bit strange to describe so I'll just mention the symptom:
bones in one armature that were constrained to bones in another
armature, which in turn were constrained to a non-armature object
weren't getting updated correctly.

This fixes bf-blender bug #955 (thanks Appolux).

Note: This commit need not be logged in future release notes (was
caused by recent armature speed ups).