cms

der: have `Reader::peek*` methods take `&mut self` #1196

Job	Run time
minimal-versions	0s
build (1.75.0, thumbv7em-none-eabi)	29s
test (1.75.0)	2m 55s
build (1.75.0, wasm32-unknown-unknown)	36s
test (stable)	2m 52s
build (stable, thumbv7em-none-eabi)	31s
build (stable, wasm32-unknown-unknown)	36s
	7m 59s

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