Help identify duplicates IDs in test suite and missing tests in id
lists.
* bzrlib/tests/test_selftest.py:
(TestTestIdList): Add tests for suite_matches_id_list.
* bzrlib/tests/__init__.py:
(suite_matches_id_list): Test id list
filtering sanity checks.
(test_suite): When id list filtering is used do some sanity
checks.