Merge latest css improvements into master #403

Job	Run time
B2 gcc-11	5m 42s
B2 clang-14	3m 48s
CMake gcc-11 17 Debug	10m 25s
B2 msvc-14.2	8m 10s
B2 msvc-14.3	7m 11s
CMake gcc-11 20 Release	10m 11s
CMake clang-11 17 Debug	1m 35s
CMake msvc-14.2 Debug C++17	7m 11s
CMake clang-11 20 Debug	1m 19s
CMake msvc-14.2 Release C++17	7m 27s
CMake clang-13 17 Release	1m 27s
CMake msvc-14.3 Debug C++20	12m 1s
CMake clang-13 20 Release	1m 55s
CMake msvc-14.3 Release C++20	7m 52s
CMake clang-14 17 Debug -stdlib=libc++	9m 10s
CMake clang-14 20 Release -stdlib=libc++	10m 52s
	1h 46m 16s

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