Implementation of GMAC #322

Job	Run time
test (1.85.0)	13s
build (stable, thumbv7em-none-eabi)	12s
build (1.85.0, wasm32-unknown-unknown)	15s
build (stable, wasm32-unknown-unknown)	15s
test (stable)	3s
build (1.85.0, thumbv7em-none-eabi)	14s
minimal-versions / minimal-versions	21s
	1m 33s

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