ws: Make test-server fail on warnings and criticals

The other tests all abort on warnings and criticals (except for
cases where these are expected). Make test-server behave similarly.
tap-driver: Update TAP harness and compiler with fixes from elsewhere

Broader use of the TAP harness and compiler has shown several
bugs which have been fixed. We can benefit from these fixes.

Make test-server detect whether running under a test harness
by using an environment variable. Using --tap argument conflicted
with how tap-gtester was running tests.

This includes fixes needed by the next commit, which brings
valgrind into play.
Makefile.am: Add 'make check-memory' target which runs valgrind

Add some basic suppressions files. These can be expanded.

No leak checking yet, that's dependent on the glib wip/gcleanup
branch and not yet ready.