fix prints to reflect what's actually being done.

a macro could do this, i'm sure...

rust/pointers.rs

        let l: List<int> = cons(1, cons(2, Nil));
        println!("l = {}", l);
        println!("cons(3, box l) = {:?}", cons(3, l));
        println!("cons(3, l) = {:?}", cons(3, l));
    }
}
        let l: &List<int> = &cons(1, nil);
        println!("l = {:?}", l);
        println!("lwr_cons_with_ref(1, l) = {:?}", cons(1, l));
        println!("cons(1, l) = {:?}", cons(1, l));
    }
}