ref: 5c5ffea92c87de9ccdde90dbca6fc345137ef9a6
dir: /sys/src/ape/lib/ap/gen/strchr.c/
#include <string.h>
char*
strchr(const char *s, int c)
{
	char c1;
	if(c == 0) {
		while(*s++)
			;
		return s-1;
	}
	while(c1 = *s++)
		if(c1 == c)
			return s-1;
	return 0;
}