P0549 Adjuncts to std::hash

[jensmaurer]

P0549R5 Adjuncts to std::hash (Walter E. Brown)

https://issues.isocpp.org/show_bug.cgi?id=264

[jensmaurer]

LWG in Kona

[wg21bot]

P0549R6 Adjuncts to std::hash (Walter E Brown)

[wg21bot]

P0549R7 Adjuncts to std::hash (Walter E Brown)

[JeffGarland]

This was reviewed on June 12th in a telecom session -- notes on Wiki below.

https://wiki.edg.com/bin/view/Wg21summer2020/D0549R8:AdjunctsToStd::hash

Waiting on suggested revisions from author.