Some tests had previously been passing despite actually causing a crash, due
to the required output being too loosely specified. This ensures the bare minimum:
that every test has an expected EXIT code and SIGNAL result.
The codes suggested were taken from the test's current output, and only applied for
CORE tests, but hand inspection suggests these choices are reasonable.
There is no need for having yet another script and directory for each
and every feature of goto-instrument.
Includes minor cleanup of test.desc files (no quotes).