add C++20 module #273

Job	Run time
ubuntu cmake	12s
windows (Win32, standard)	2m 3s
macos cmake	14s
ubuntu (g++, standard)	1m 8s
windows (Win32, PUGIXML_WCHAR_MODE)	2m 4s
windows (Win32, PUGIXML_COMPACT)	2m 8s
ubuntu (g++, PUGIXML_WCHAR_MODE)	1m 8s
windows (Win32, PUGIXML_NO_EXCEPTIONS)	1m 11s
ubuntu (g++, PUGIXML_COMPACT)	1m 14s
windows (Win32, PUGIXML_STRING_VIEW)	2m 8s
ubuntu (g++, PUGIXML_NO_EXCEPTIONS)	1m 1s
windows (x64, standard)	1m 14s
ubuntu (g++, PUGIXML_STRING_VIEW)	1m 6s
windows (x64, PUGIXML_WCHAR_MODE)	2m 49s
ubuntu (clang++, standard)	55s
windows (x64, PUGIXML_COMPACT)	2m 2s
ubuntu (clang++, PUGIXML_WCHAR_MODE)	51s
windows (x64, PUGIXML_NO_EXCEPTIONS)	1m 58s
ubuntu (clang++, PUGIXML_COMPACT)	55s
windows (x64, PUGIXML_STRING_VIEW)	2m 44s
ubuntu (clang++, PUGIXML_NO_EXCEPTIONS)	52s
ubuntu (clang++, PUGIXML_STRING_VIEW)	48s
macos (clang++, standard)	51s
macos (clang++, PUGIXML_WCHAR_MODE)	46s
macos (clang++, PUGIXML_COMPACT)	58s
macos (clang++, PUGIXML_NO_EXCEPTIONS)	47s
macos (clang++, PUGIXML_STRING_VIEW)	43s
	34m 50s

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