add broken from_iterator.

rust/pointers.rs

        }
    }
    // pub fn from_iterator<'a, I: Iterator<A>, A: 'a>(mut i: I) -> &'a List<'a A> {
    //     let mut xs = &Nil;
    //     for x in i {
    //         xs = &cons(x, xs);
    //     }
    //     xs
    // }
    pub fn run() {
        println!("\nlist_with_ref:");