Implements parts of P1614, including synth-three-way and three way comparison for std::pair.
Reviewed By: #libc, Quuxplusone, Mordante
Differential Revision: https://reviews.llvm.org/D107721
Mark the now-done [cmp.result] in spaceship projects as complete;
normalize some status markers for papers and projects; fix alignment
and line breaks in spaceship projects, add links to standard
Differential Revision: https://reviews.llvm.org/D108502
Add issue tracking and assignment for the implementation of P1614R2: The Mothership has Landed.
Reviewed By: cjdb, #libc, Mordante, Quuxplusone
Differential Revision: https://reviews.llvm.org/D107877
Kent Ross