Adapt to c++ change P1423R2 if detected.

[ma30002000]

When compiling hippomocks with gcc 10 with the c++ standard set to c++20, the following compile error occurs:

hippomocks.h:479:6: error: use of deleted function ‘std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const wchar_t*) [with _Traits = std::char_traits<char>]’

This is due to P1423R2 removing the basic_ostream<char>::operator<< overloads for wchar_t* due to its unexpected behavior.

See [https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1423r2.html#option7].