Add missing symbols #2788

Job	Run time
cargo clippy	13s
cargo +stable build	30s
cargo +1.36 build (futures-{core, io, sink})	1m 27s
cargo bench	20s
cargo +beta build	23s
cargo doc	16s
cargo +nightly build	29s
cargo hack check --feature-powerset	18s
cargo fmt	16s
cargo minimal-versions build	25s
cargo miri test	33s
cargo build --target thumbv7m-none-eabi	20s
cargo test -Z sanitizer=address	41s
cargo build --target thumbv6m-none-eabi	16s
cargo test -Z sanitizer=memory	37s
cargo +1.56 build	2m 13s
cargo test (ubuntu-latest)	17s
cargo test -Z sanitizer=thread	35s
cargo test (macos-latest)	22s
cargo test (windows-latest)	44s
cargo test (ubuntu-latest, aarch64-unknown-linux-gnu)	52s
cargo test (ubuntu-latest, armv7-unknown-linux-gnueabihf)	41s
cargo test (ubuntu-latest, armv5te-unknown-linux-gnueabi)	45s
cargo test (ubuntu-latest, i686-unknown-linux-gnu)	49s
	14m 22s

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