Effects: Constructs a move_iterator, value initializing current. Iterator operations applied to the resulting iterator have defined behavior if and only if the corresponding operations are defined on a value-initialized iterator of type Iterator.
explicit move_iterator(Iterator i);
Effects: Constructs a move_iterator, initializing current with i.
template <class U> move_iterator(const move_iterator<U>& u);
Effects: Constructs a move_iterator, initializing current with u.base().
Requires: U shall be convertible to Iterator.