gcc2 was relying on the c99 functions being there, but they are not in
the std namespace.
* Disable the C99 functions and macros in C++ mode
* Redefine them as inline functions in cmath in the std namespace.
Fixes#7396.
- this differs slightly from the one that lives in buildtools/gcc as it
has been "ported" to the newer libio that haiku uses as part of its own
libroot
git-svn-id: file:///srv/svn/repos/haiku/trunk/current@9906 a95241bf-73f2-0310-859d-f6bbb57e9c96