SPV-in workaround for row-major matrices

[kvark]

Fixes #675
I admit, this is a real PITA, and this code reflects it.

The workaround I wanted to implement was to issue an Load into the matrix if we see it being row-major, followed by Transpose, then pretending that it was column-major all this time.
The problem is that there are many ways to cross that "ima matrix" barrier:

• OpAccessChain doesn't have intermediate IDs, so we can't do it iteratively
• it may start high up and end on a matrix, or on an element of it
• it turns out, an array of matrices, when being a struct field, can also have this row-major decoration

If anybody can have a better idea, I'd love to consider it!

[Timo-DK]

LGTM, thanks! It is quite some complexity to "only' support basically a matrix agnostically. I have no idea how to improve upon this.