9.1275 wcwidth

POSIX specification:
https://pubs.opengroup.org/onlinepubs/9699919799/functions/wcwidth.html

Gnulib module: wcwidth

Portability problems fixed by Gnulib:

• This function is missing on some platforms: Minix 3.1.8, mingw, MSVC 14.
• This function is not declared (without -D_GNU_SOURCE) on some platforms: glibc 2.8.
• This function handles combining characters in UTF-8 locales incorrectly on some platforms: NetBSD 9.0, OpenBSD 5.8.
• This function returns 2 for characters with ambiguous east asian width, even in Western locales, on some platforms: Solaris 11.4.

Portability problems not fixed by Gnulib:

• On Windows and 32-bit AIX platforms, wchar_t is a 16-bit type and therefore cannot accommodate all Unicode characters.
• This function treats zero-width spaces like control characters on some platforms: AIX 7.2.