Back in 2004, Peter Moulder added assert_close to nr-matrix.cpp and used in it several matrix operators in libnr (such as multuplying a matrix by a scale, etc). All it does is just checks if two matrices are "close enough".

I am going to remove this assert because:

- what it tests is simply computer arithmetic, not something Inkscape itself can get wrong. I don't think it can discover any bugs for us.

- used in basic operators, it likely slows the program down for no gain whatsoever.

Unless there are objections, of course.