They jumped him when he was walking past an alley, a couple of blocks from the stockyards on Chicago's brawling South Side. He had gotten off the "El" two stops down because it was a damn fine Spring morning and he liked to walk through the Polish section and watch the city wake up. He was 17 years old and he hadn't grown cynical with the world yet. He liked the clean, fresh smell of the early morning and he got a kick out of the sleepy-eyed housewives in their ratty bathrobes, banging open the