Blender Git Loki

Fix T57767: Pivot point broken after scaling to 0 in a dimension

matrix inversion was changed in rB01c75c3765eb from own code to EIGEN
for performance reasons. EIGEN would return a zero matrix on failure
(resulting in the pivot always being at the object origin).
This brings back the "old" matrix inversion code (which has the benifit
of providing a partial solution which makes the local transform center
appear correct)

Reviewers: campbellbarton

Maniphest Tasks: T57767

Differential Revision: https://developer.blender.org/D4804