Verify that every test file which references a harness file using the
"includes" directive also contains at least one reference to a value
defined in the harness file.
To support this check, extend each harness file with a list of values
which it defines.
Previously, the error message generated by failed asynchronous tests was
generic and underspecified. Improve the format and explicitly document
it in project's interpreting guidelines.
Mike Pennisi
Rick Waldron
Mathias Bynens
Brian Terlson