* libc/stdio/vfprintf.c: Include ../stdlib/local.h. Replace call to

	* libc/stdio/vfprintf.c: Include ../stdlib/local.h.  Replace call to
	_mbtowc_r with direct call to __mbtowc.
	* libc/stdio/vfscanf.c: Ditto.
	* libc/stdlib/btowc.c: Include local.h.  Replace call to _mbtowc_r
	with direct call to __mbtowc.
	* libc/stdlib/mblen.c: Ditto.
	* libc/stdlib/mblen_r.c: Ditto.
	* libc/stdlib/mbrtowc.c: Ditto.
	* libc/stdlib/mbstowcs_r.c: Ditto.
	* libc/stdlib/mbtowc.c: Ditto.
	* libc/stdlib/wcrtomb.c: Include local.h.  Replace call to _wctomb_r
	with direct call to __wctomb.
	* libc/stdlib/wcsnrtombs.c: Ditto.
	(_wcsnrtombs_r): Ditto.
	* libc/stdlib/wcstombs_r.c: Ditto.
	* libc/stdlib/wctob.c: Ditto.
	* libc/stdlib/wctomb.c: Ditto.

	* libc/stdlib/mbrtowc.c (mbrtowc): Implement independently from
	_mbrtowc_r, unless PREFER_SIZE_OVER_SPEED or __OPTIMIZE_SIZE__ are
	defined.
	* libc/stdlib/wcrtomb.c (wcrtomb): Implement independently from
	_wcrtomb_r, unless PREFER_SIZE_OVER_SPEED or __OPTIMIZE_SIZE__ are
	defined.

	* libc/stdlib/mbtowc_r.c (__utf8_mbtowc): Drop unnecessary test for
	ch >= 0.