[patch] C++ FE warning control cleanup

[Gabriel Dos Reis]

Lee Millward <lee.millward@gmail.com> writes:

| 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 important thing is that we fix them as we find them, as soon as
possible. 

What your patch did was to unconver a mismatch between documentations
and uses in various parts of the compiler, e.g. -fconst-string,
-Wwrite-strings, option_enables().

-fconst-string has been declared obsolete for while, maybe it is time
 for it to go.

-- Gaby