P3790 R0 Pointer lifetime-end zap proposed solutions: Bag-of-bits pointer class

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P3790R0 Pointer lifetime-end zap proposed solutions: Bag-of-bits pointer class (Paul E. McKenney, Maged Michael, Jens Maurer, Peter Sewell, Hans Boehm, Hubert Tong, Niall Douglas, Thomas Rodgers, Will Deacon, Michael Wong, David Goldblatt, Kostya Serebryany, Anthony Williams, Tom Scogland, JF Bastien, and Daniel Krügler.)