* A patch to make sure that constraints on bones that point to
external objects are evaluated correctly (and that the bones that
depend on these bones are evaluated correctly, etc, ad nauseum).
This addresses some of intrr's issues (the blender-related ones,
that is).
* Make sure that deformed displists are updated when the user
manipulates any of the constraint buttons.
* Added a nice little function, ik_chain_looper(), that executes a
callback for every bone in an IK chain.
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