This is a very simple testing framework for writing and running tests
for C++. The basic idea is that a `struct unit_test` is defined for
every test function to run, and then the test framework simply runs them
one at a time, printing various information about the tests out as ti
goes.
There are also various 'test_assert*()` macros to assert the value of
things while running the tests. They verify a value is equal to an
expected value, and if not it fails the tests. The more specific
assertions like the `ints` and `buffers` ones also print out useful
information on what the expected and actual values were, to aide in
debugging.
