[Bug libstdc++/113318] [C++26] Implement P1885R12, Naming text encodings to demystify them

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113318

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I have a patch to add partial std::text_encoding support on Windows, using
GetACP() and _MSVC_EXECUTION_CHARACTER_SET to query the system codepage and the
execution charset codepage, and then mapping from Windows codepage identifiers
to IANA mib values.