uchar.h: only define char32_t and char16_t before c++11 found while testing libc++ https://en.cppreference.com/cpp/keyword/char16_t https://en.cppreference.com/cpp/keyword/char32_t add _wint_t.h and _mbstate_t.h Change-Id: Ia5529cc9aa7316e091297f9842c3007a855f813e Reviewed-on: https://review.haiku-os.org/c/haiku/+/11346 Reviewed-by: Adrien Destugues <[email protected]> Tested-by: Commit checker robot <[email protected]> Reviewed-by: Jérôme Duval <[email protected]> (cherry picked from commit bf1e1da47d6181dbf8122bc52801c08968e1a4ed) Reviewed-on: https://review.haiku-os.org/c/haiku/+/11374 Reviewed-by: waddlesplash <[email protected]>