move_iterator::operator* should be defined in terms of iter_move

[ericniebler]

Proposed Resolution:

Change the synopsis of class move_iterator in [move.iterator]:

template <InputIterator I>
class move_iterator {
public:
  using iterator_type = I;
  using difference_type = difference_type_t<I>;
  using value_type = value_type_t<I>;
  using iterator_category = input_iterator_tag;
-  using reference = see below ;
+  using reference = rvalue_reference_t<I>;
  move_iterator();
  explicit move_iterator(I i);
  [...]
};

Delete paragraph 1:

- 1 Let R be reference_t<I>. If is_reference<R>::value is true, the template
-   specialization move_iterator<I> shall define the nested type named reference as a
-   synonym for remove_reference_t<R>&&, otherwise as a synonym for R.

Change the description of move_iterator::operator* in [move.iter.op.star] as follows:

- 1 Effects: Equivalent to static_cast<reference>(*current).
+ 1 Effects: Equivalent to: return iter_move(current);

[ericniebler]

We forgot that i[n] should be changed to return iter_move(i + n). Considering that the op* change was approved, I consider the corresponding change to op[] to be editorial/approved in principle. We should note the edit in the Editor's Report for Kona.

[ericniebler]

See e70a378.