ref: a3c75553b4c50247ce22a4da4d2a87c10d5b0835
dir: /sys/src/libc/port/strchr.c/
#include <u.h>
#include <libc.h>
char*
strchr(char *s, int c)
{
	char r;
	if(c == 0)
		while(*s++)
			;
	else
		while((r = *s++) != c)
			if(r == 0)
				return 0;
	return s-1;
}