Remove unecessary and broken MC/DC compile test

Remove unecessary and broken MC/DC compile test

The __sigsetjmp test was added as a regression test in an early
iteration of the MC/DC support, as it caused an internal compiler error.
This was triggered by a code path which did not make it through to the
final revision.  Since this test really only worked on systems with
__sigsetjmp, and does not serve a purpose any more it can be removed.

gcc/testsuite/ChangeLog:

	* gcc.misc-tests/gcov-19.c: Remove test.