[patch] C++ FE warning control cleanup

[Lee Millward]

I can assure you that I did follow the testing procedure outlined on
this page - http://gcc.gnu.org/contribute.html#testing and kept the
original test suite results to compare with those after my patch which
didn't report any new failures.

The fact that my patch did cause these numerous regressions is
something I sincerely apologise for to everyone affected for the
inconvienence caused.

Lee.