[PATCH] c++-types-check: Do not run this test if there is no C++ support

[Roland McGrath]

Follow the example of tst-chk4 et al in debug/Makefile.  That is, just add
it to tests-unsupported.  There is no need to conditionalize adding it to
tests or tests-special per se.  But if it's in tests-unsupported it can't
have an explicit foo.out rule, so for this case conditionalizing its
addition to tests-special along with the explicit rule makes sense.