Blender Git Loki

Bugfix #5038

The "Copy Size" constraint was calling a where_is_object(), this caused
the depsgraph to mess up in very weird ways and rare occasions. In the
sample file it showed strange lags in bones for using the "Stride bone"
option.

While trying to locate the bug I've revisited the Pose depsgraph in detail,
trying to figure out how it can print possible cycle errors in dependency.
That has been added now too (in console). Unfortunately the bugreport
example had no cycle errors. :)