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
036e95bb21