Blender Git Loki

Fix T80970: Copy Rotation constraint incorrect under shear

Orthogonalize the constraint target's matrix before decomposing it into
Euler angles. This removes sheer, and is actually a requirement for
correct decomposition.

It's conceivable that someone has used the incorrect behaviour in a rig.
As the shear caused unpredictable flipping of the constrained object,
this is unlikely.

Reviewed By: angavrilov, sybren

Differential Revision: https://developer.blender.org/D8915