experimental negative value support #422

Job	Run time
Build (gcc-13/make on macos-13)	35s
Build (clang-18/bmake on ubuntu-22.04)	31s
Build (gcc-14/make on ubuntu-24.04)	30s
Build (musl-gcc/bmake on ubuntu-22.04)	59s
Build (gcc-14/bmake on macos-14)	20s
Build (clang-18/bsdmake on macos-15)	26s
	3m 21s

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