Minor fixes to unit-testing.scm.

Minor fixes to unit-testing.scm.

- Update copyright years.
- Ignore unused variable CONDITION in ASSERT-ERROR.
- Use RUN-SUB-TEST to run test procedures in RUN-SUB-TESTS

The last one is probably wrong, but without it, running unit tests
crashes in a bizarre way for me.  Example:

(run-unit-tests "runtime/test-ephemeron")
;Loading "runtime/test-ephemeron.com"... done
no-gc: failed 2 sub-tests out of 2 in .32 seconds:
    .0.0:
;Ill-formed failure: key