Add TODO test for cleanup bug in parsing failure

This currently breaks weirdly:

        $ perl -Mop -e 'class cat { method meow {}, }'
        syntax error at -e line 1, near "},"
        Undefined subroutine called at -e line 1.
        Attempt to free unreferenced scalar: SV 0x1ce61a0 at -e line 1.

Included is a few tests (that will need fixing up with proper errors) to illustrate this test, currently under a TODO.