The f12e9f32b5 patch introduced a new improved method of blending
dual quaternion transformations to handle combined scale and rotation
better. However, the changes were not complete:
* The new math ignored crazyspace computations, which need to compute
a complete transformation matrix. As an optimization, the new method
avoided fully computing the scale component, so the matrix would
have no scale or shear.
* The Armature constraint is supposed to behave identically to the
modifier, and it was not updated. The constraint also requires
computing a complete matrix.
This change extracts the new math into a utility function, change
the optimization to be controlled by a parameter, and use the new
function in the constraint.
Alexander Gavrilov