Regression test utility

A generic test program was written, that generates a system holding pseudo-random numbers, solves it using the optimized code, and finally checks the $\mathbf{A}x - b$ residual. The test utility is trivial but should catch most errors anyway.

I have of course tested the generated solvers for numerous systems, and it is my belief, that the optimizer and code generator behaves correctly for any given (valid) system.

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