* wcsmbs/wctob.c (wctob): Make buf array of unsigned char.

* wcsmbs/wctob.c (wctob): Make buf array of unsigned char.

	* sysdeps/generic/strchrnul.c: Add cast to avoid warning.
	* libio/iofwide.c: Add casts to avoid warnings.
	* stdio-common/printf-prs.c (parse_printf_format): Introduce new
	variable f to avoid warnings.
	* sysdeps/unix/sysv/linux/x86_64/makecontext.c (__makecontext):
	Fix a few casts to avoid warnings.
	* iconv/gconv_simple.c (internal_utf8_loop): Make start unsigned
	to avoid warning.