s/BoxedListIterator/Items/ -> ack!

As for the lifetime parameter, it is not because of @, but because of ```current```, which gets only a reference for @List<T>, and thus requires a lifetime specifier (as warned by the compiler):
```
/Users/bruno.d/Work/rust/src/libcollections/list.rs:28:19: 28:32 error: missing lifetime specifier
/Users/bruno.d/Work/rust/src/libcollections/list.rs:28     priv current: &BoxedList<T>,
```