Enhance test suite.

[andrewchambers]

I would like negative tests (test pass on failure), tests in sub directories and selective test running.
It is probably best to parse some sort of heading or meta data file to get the test information.

We should study what GCC and Clang do, with the hope of being able to drop their tests into ours with a symlink, while keeping their tests separate from ours.

Another form of testing is just to compare our results with the results of other compilers. The downside is speed.