Switched tests to using matrix_t* accessor macros
Switched tests to using matrix_t* accessor macros

At first I was against it, because poorly-written macro magic
could ruin our tests... but if I want to change the way we access
data, then I have to change all of our tests.

So now I have transformed the existing test suite. I will have to
write some tests explicitly for the macros later on.

jamesmishra/scalarstop