Display *why* a common-test-suite test failed

This is good, because it's easier to debug a problem if you know *why*
there's a problem.  On the other hand, for some reason :record_errors =>
true causes a *lot* more test cases to fail, to the point where no file in
the common test suite is completely free of errors -- hence all files are
ignord, and no test cases are actually being run.

I guess what's going to have to happen is that someone deletes one file
from the IGNORED_TESTS list, fixes up all the failures in that file, and
then moves on to the next.  Bags not me.