Bring back test.deparse make target, and make it smarter.

t/TEST now allows skipping / ignoring test failures under test.deparse.

 * Known bad tests can be skipped entirely (not loaded/run)
 * Known failing tests can be run and checked for a change in state.

   - If they fail as expected, they are skipped
   - If they pass, the test is forced to fail so the report at the end is
     useful.