Enhance test framework

Make it possible to mark known failues, and ignore specific tests.
This then makes it possible to tell the difference between expected
and unexpected failures.
Fix scenario for issue #32

The test code was broken and didn't compile, when it should have.
Apparently the test actually passes, so the issue was presumably fixed
by the stdlib improvements that have been made.

Fixes #32
Mark issue #17 as a known bug

Now that we have the facility to do so.