[Bug libstdc++/126111] std module unconditionally exports wchar_t-related names when configured with --disable-wchar_t

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126111

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Sebastian Jude from comment #1)
> Just stumbled upon a very similar issue with
> 
> using std::stold;
> 
> which might need a #if (_GLIBCXX_HAVE_STRTOLD && !
> _GLIBCXX_HAVE_BROKEN_STRTOLD) guard.

Or don't try to use C++20 modules on broken operating systems that don't
support C99.

The wchar guards are worth adding.