MeshMaker now can be told not to attempt vertex merging.

Useful for when you want to build faceted models, rather than smoothing.
Existing code should not see any difference.
Proper invert for 3x3 matrix.

Previously, the vsMatrix3x3::Invert() and Inverse() functions actually
performed a transpose (since that's faster to calculate for rotation
matrices, which is what you usually put in a vsMatrix3x3).  However, it
wasn't a real, generic invert.

I've now implemented a proper invert, and moved the old, fast "basically
the same as an invert for rotation matrices" over to 'Transpose()'.
Nothing inside VectorStorm was calling that function anyway, and I only
had one spot in a game which was calling it (and even that was old code
which was no longer in use).  Hopefully this shouldn't affect anyone.