Add extension macros as constexpr #849

Job	Run time
build (windows-latest, x86, Debug, 11)	12m 25s
build (windows-latest, x86, Debug, 14)	10m 45s
build (windows-latest, x86, Debug, 17)	11m 59s
build (windows-latest, x86, Debug, 20)	13m 43s
build (windows-latest, x86, Release, 11)	12m 55s
build (windows-latest, x86, Release, 14)	12m 38s
build (windows-latest, x86, Release, 17)	12m 51s
build (windows-latest, x86, Release, 20)	10m 37s
build (windows-latest, x64, Debug, 11)	11m 2s
build (windows-latest, x64, Debug, 14)	11m 40s
build (windows-latest, x64, Debug, 17)	10m 21s
build (windows-latest, x64, Debug, 20)	11m 34s
build (windows-latest, x64, Release, 11)	12m 12s
build (windows-latest, x64, Release, 14)	11m 38s
build (windows-latest, x64, Release, 17)	9m 32s
build (windows-latest, x64, Release, 20)	11m 54s
build (windows-2019, x86, Debug, 11)	12m 2s
build (windows-2019, x86, Debug, 14)	11m 15s
build (windows-2019, x86, Debug, 17)	10m 29s
build (windows-2019, x86, Debug, 20)	10m 13s
build (windows-2019, x86, Release, 11)	10m 59s
build (windows-2019, x86, Release, 14)	13m 15s
build (windows-2019, x86, Release, 17)	10m 37s
build (windows-2019, x86, Release, 20)	10m 3s
build (windows-2019, x64, Debug, 11)	13m 7s
build (windows-2019, x64, Debug, 14)	13m 41s
build (windows-2019, x64, Debug, 17)	10m 58s
build (windows-2019, x64, Debug, 20)	10m 9s
build (windows-2019, x64, Release, 11)	12m 16s
build (windows-2019, x64, Release, 14)	13m 15s
build (windows-2019, x64, Release, 17)	12m 35s
build (windows-2019, x64, Release, 20)	12m 25s
	6h 15m 5s

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