* libc/string/local.h: New file.
* libc/string/wcswidth.c (wcswidth): Convert japanese wide
characters to Unicode here. Handle surrogate pairs for UTF-16
systems. Call __wcwidth rather than wcwidth.
* libc/string/wcwidth.c: New implementation using Markus Kuhn's
wcwidth implementation for Unicode.
(bisearch): New static function.
(__wcwidth): New function. Take wint_t rather than wchar_t as
parameter to allow full Unicode handling on UTF-16 systems.
Move old wcwidth implementation here for non-multibyte aware
systems.
(wcwidth): Convert japanese wide characters to Unicode here.
Call __wcwidth rather than using iswprint/iswcntrl.