message: Make VectorRefIterator clonable
diff: @@ -63,6 +63,7 @@ impl<T: VectorElement> ExactSizeIterator for VectorIterator<T> where Vector<T>:
  impl<T: VectorElement> FusedIterator for VectorIterator<T> where Vector<T>: VectorExtern<T> {}
  +#[derive(Clone)]
  pub struct VectorRefIterator<'v, T: VectorElement> where Vector<T>: VectorExtern<T> {
  vec: &'v Vector<T>,
  i: size_t,
  