chg: dev: Restore the ability to select individual unit tests

This adds the command line arguments: -d (debug), -l (list tests) and -t test (run this test) to the unit tests.

e.g.

    % ./rdata_test -t zonemd
    [==========] selected: Running 1 test(s).
    [ RUN      ] zonemd
    [       OK ] zonemd
    [==========] selected: 1 test(s) run.
    [  PASSED  ] 1 test(s).
    % 

Closes #4579 (closed)