US163 16.05.3.5 [allocator. requirements] Default behavior for "construct" is "construct_at" LWG 3315

[wg21bot]

The default behavior for a.construct is now to call construct_at

Proposed change:
Replace "default" entry with:
construct_at(c, std::forward<Args>(args)...)

[dietmarkuehl]

Reviewed Monday morning in Belfast in LWG small group session.

[Dani-Hub]

The associated issue is LWG 3315

[JeffGarland]

Reviewed and approved by LWG full group during Wed morning issue processing in Belfast. LWG 3315 set to Ready.