cmp: stop allocating for byte printing #18

Job	Run time
cargo fmt --all -- --check	7s
cargo test (ubuntu-latest)	40s
cargo clippy -- -D warnings (ubuntu-latest)	16s
cargo test (windows-latest)	3m 57s
cargo test (macOS-latest)	2m 25s
Code Coverage (windows-latest, windows)	6m 58s
cargo check (windows-latest)	36s
cargo check (macOS-latest)	13s
cargo clippy -- -D warnings (macOS-latest)	15s
GNU test suite	50s
cargo clippy -- -D warnings (windows-latest)	52s
Code Coverage (macos-latest, macos)	2m 34s
cargo check (ubuntu-latest)	14s
Code Coverage (ubuntu-latest, unix)	1m 52s
	21m 49s

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