Tidy up output of selftest in num/termination

More fixes given testutils API change

Revert "Put variant regression test into tfl's selftest"

This reverts commit 2a25e6b67662cae9559c5ab0952fb64ff5aabd1a.

This test requires lists, which aren't yet built at the time this
particular test is run.

Put variant regression test into tfl's selftest

There are variations on this theme in src/tfl/examples/variant, but
that file is not tested by the selftest machinery.

Fix many selftests to have prettier output

Add tests for commit 9d6174e.

Needed to update the Holmakefile to get the tests to run.

Fix a bug preventing TFL schema variables from being called "x".

The same problem led to inscrutable errors when attempting to define a
normal function (there should just be a "there is a free variable on
the RHS" error in this case).

Another test catching a bug introduced by case-const arg-flip.

This is ongoing progress with really getting issue #97 resolved.

Test demonstrating bug in Define with literal patterns.

This is a consequence of case-const arg-flipping of course.

A new test for mutually recursive function definition.

There is already a test that tweaks the bug I am seeing in
src/datatype, but that depends on a mutually recursive datatype so I
figured it was a good idea to get at the functionality without the
datatype issue being required.