This creates a new test suite driver and infrastructure for going
forward. This cleans up the descriptions for tests, and is more
extensible.
Include documentation for the new engine, so that new tests can go
here instead of the old test suite.
By adding ivtest to the iverilog source tree, it is easier to keep
the regression test synchronized with the source that is being tested.
This should be especially helpful for PRs that add a new feature, and
have a matching ivtest PR with the regression test for that feature.
Cary R
Stephen Williams