Describe the needed test cases, and implement a couple Test::Class features.
* Run all subs matching /^test_*/ (for which we can plan)...
* Unless TEST_METHOD is set, in which case run matching subs (sans plan).
* Define total number of tests very near 'use Test::More', where expected.
* Define test tempdir where it's declared, no longer any reason why not.
* Move most comments from TODO.cvs into t/cvs.t.
* Add a whole bunch more comments describing the needed test cases.
XXX existing tests are order-dependent, but currently happen to pass