Halfway fix some broken tests.

Halfway fix some broken tests.

- Use with-test-properties, not run-sub-test.

- Disable run-sub-test in the test environment; it doesn't make sense
  for tests to call it.

- Add a rudimentary expect-failure.  (Feel free to spruce this up
  with a message detailing the nature of the expectation, a note in
  the final report, &c.)

- Partly fix test-char-set.scm, which was silently nonfunctional
  because of run-sub-test.  Leave an xfail for the part I don't know
  how to fix.  (Chris -- if you could fix this, that would be great!)