Build: Remove unneeded glib unit test files.

Strip down mk/glib-tap.mk to almost nothing. All it's really there for
now is to define LOG_DRIVER and LOG_COMPILER. We could add other test
related stuff to it later if needed. We didn't need any of the
installed vs. uninstalled unit test stuff, nor the test_data and
dist_test_data stuff. We only support running unit tests from the
source tree.

Because it doesn't really do anything anymore, rename it to mk/tap.mk.
With that gone, we no longer need support for the ./configure options
that were set up by m4/glibtests.m4, so that entire file can go. And
then with that gone, we don't need to call GLIB_TESTS anymore.

Then, all the test directory Makefile.am files need to be changed. Get
rid of the test_data and dist_test_data blocks. Remove the comment
referring to glib documentation. Put all the tests into check_PROGRAMS
and then set TESTS equal to that. glib-tap.mk was doing that for us,
but since we no longer have that file we need to do it manually.