P2406 Fix counted_iterator interaction with input iterators

[wg21bot]

P2406R0 Fix counted_iterator interaction with input iterators (Yehezkel Bernat, Yehuda Bernat)

[brycelelbach]

@inbal2l please schedule this.

[brycelelbach]

Did this fall through the cracks?

[inbal2l]

No. The authors are working on R1, they believe the solution proposed in R0 is not correct. I've encouraged them to pursue this (as I do believe this is an important fix) but they did not want to pursue it for 23 for a lack of time. I've also asked a member of SG9 to assist with finalizing R1, but I'm not aware of any progress there. I will, however, ask the authors (again) to present in Kona, hoping that the group will be able to finalize the proposed solution. We will dedicate the (pre-Kona) near NB meeting to assisting them as well.