Merge pull request #221 from boostorg/develop #545

Job	Run time
B2 msvc-14.2	7m 28s
CMake msvc-14.2 Debug C++17	7m 2s
B2 msvc-14.3	7m 36s
CMake gcc-11 17 Debug	9m 37s
CMake msvc-14.2 Release C++17	7m 10s
B2 gcc-11	5m 7s
CMake gcc-11 20 Release	11m 58s
CMake msvc-14.3 Debug C++20	9m 58s
CMake clang-11 17 Debug	6m 11s
B2 clang-14	5m 31s
CMake msvc-14.3 Release C++20	8m 22s
CMake clang-11 20 Debug	6m 42s
CMake clang-13 17 Release	9m 30s
CMake clang-13 20 Release	9m 41s
CMake clang-14 17 Debug -stdlib=libc++	8m 31s
CMake clang-14 20 Release -stdlib=libc++	12m 24s
	2h 12m 48s

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