Things this commit does in the process of rewriting the testing
infrastructure:

  - argument parsing and per-file option handling has been factored out
    into separate functions to avoid duplication;
  - macros have been replaced with functions;
  - all languages use the same structure (add the tests, then build the
    executable);
  - -E## support has been removed; use ${testname}_ARGS instead;
  - some style cleanups;
  - replace directory properties with variables so that multiple test
    sets may be made at one time;
  - set test labels from the TEST_LABELS module.cmake option.

Change-Id: Ic75023208725e5c09043feabdf758014b66fa26e