Blender Git Loki

Bugfix #5022

If you rename a Constraint, the used Constraint Channels (Ipo curves) were
not renamed as well, making animations not work anymore.

Now renaming works up to this level:
- own object constraints
- own object Action constraints

This is identical to Bone renaming. Note that other actions (like in NLA)
are not corrected for renaming. Have to look at ways to provide that once.