Disabled a function that doesn't work with the new Num instance for lists

Pascal stopped working
I’ll add the other way to calculate it later
More linear functions!

Cleaned up matrix multiplication a bit, added asserts instead of the
messier error system I had been using, added code to multiply vector *
matrix, and some infix functions for it
Added some functions around the identity matrix

So we’ve got identity, which generates an infinite lazy identity
matrix, and mkIdentity which takes an int and makes an n x n square
identity matrix
Added missed lines + gaussian elimination

Some lines of my code hadn’t gotten included here, dunno why
But, more importantly, elimination!  We has it!
Sure, it’s inefficient.  I’ll be adding a more efficient version of
this later.  For now, Gaussian will do.