Fix issue-210. (not ready to merge) #524

Job	Run time
B2 gcc-11	5m 2s
B2 msvc-14.2	10m 30s
CMake msvc-14.2 Debug C++17	9m 29s
B2 clang-14	5m 15s
B2 msvc-14.3	9m 40s
CMake gcc-11 17 Debug	8m 52s
CMake msvc-14.2 Release C++17	9m 56s
CMake gcc-11 20 Release	11m 28s
CMake msvc-14.3 Debug C++20	6m 34s
CMake clang-11 17 Debug	6m 42s
CMake clang-11 20 Debug	7m 3s
CMake clang-13 17 Release	9m 50s
CMake msvc-14.3 Release C++20	6m 54s
CMake clang-13 20 Release	9m 56s
CMake clang-14 17 Debug -stdlib=libc++	8m 21s
CMake clang-14 20 Release -stdlib=libc++	12m 22s
	2h 17m 54s

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