Adds <compare> library support for the spaceship operator.
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P0515R3Consistent comparisonAlbuquerque 2017P0905R1Symmetry for spaceshipJacksonville 2018P1120R0Consistency improvements for
<=> and other comparison operatorsRapperswil 2018P1185R2<=> != ==Kona 2019P1186R3When do you actually use <=>?Cologne 2019P1614R2The mothership has landedCologne 2019All 13 papers in Three-way comparison (<=>) →