Work around 'unreferenced function' warnings in NO_STL builds #223

Job	Run time
ubuntu (g++, standard)	54s
windows (Win32, standard)	1m 29s
windows (Win32, PUGIXML_WCHAR_MODE)	1m 2s
ubuntu (g++, PUGIXML_WCHAR_MODE)	58s
windows (Win32, PUGIXML_COMPACT)	1m 46s
ubuntu (g++, PUGIXML_COMPACT)	1m 0s
windows (Win32, PUGIXML_NO_EXCEPTIONS)	1m 5s
ubuntu (g++, PUGIXML_NO_EXCEPTIONS)	49s
windows (x64, standard)	1m 35s
ubuntu (clang++, standard)	40s
windows (x64, PUGIXML_WCHAR_MODE)	1m 35s
ubuntu (clang++, PUGIXML_WCHAR_MODE)	43s
windows (x64, PUGIXML_COMPACT)	1m 49s
ubuntu (clang++, PUGIXML_COMPACT)	39s
windows (x64, PUGIXML_NO_EXCEPTIONS)	1m 32s
ubuntu (clang++, PUGIXML_NO_EXCEPTIONS)	36s
macos (clang++, standard)	40s
macos (clang++, PUGIXML_WCHAR_MODE)	46s
macos (clang++, PUGIXML_COMPACT)	54s
macos (clang++, PUGIXML_NO_EXCEPTIONS)	39s
	21m 11s

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