add missing poundsMass method #2865

Job	Run time
Windows x64 MinGW Clang gnustep-2.2	27m 56s
Rocky Linux 8 x64 Clang gnustep-2.2	2m 27s
Ubuntu x64 GCC	5m 18s
Windows x64 MSVC Clang gnustep-2.2	21m 57s
Rocky Linux 9 x64 Clang gnustep-2.2	5m 20s
Windows arm64 MSVC Clang gnustep-2.2	37m 26s
Windows x64 MinGW GCC	28m 13s
Ubuntu x64 Clang gnustep-2.2	5m 11s
	2h 13m 48s

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