Add support for sendmmsg/recvmmsg #1013

Job	Run time
Check (armv7-sony-vita-newlibeabihf)	32s
Check (i686-unknown-hurd-gnu)	34s
Clippy	16s
Check (aarch64-apple-ios)	15s
Check (aarch64-linux-android)	18s
Docs (aarch64-apple-ios)	14s
Rustfmt	13s
Check (x86_64-apple-darwin)	25s
Docs (aarch64-linux-android)	16s
Check (x86_64-unknown-fuchsia)	22s
Test (stable)	23s
Docs (x86_64-apple-darwin)	14s
Check (x86_64-pc-windows-msvc)	23s
Test (1.63.0)	3m 10s
Docs (x86_64-unknown-fuchsia)	15s
Check (x86_64-pc-solaris)	14s
Test (beta)	20s
Docs (x86_64-pc-windows-msvc)	14s
Test (nightly)	22s
Check (x86_64-unknown-freebsd)	19s
Docs (x86_64-pc-solaris)	15s
Test (macos)	32s
Check (x86_64-unknown-illumos)	18s
Docs (x86_64-unknown-freebsd)	13s
Test (windows)	1m 38s
Check (x86_64-unknown-linux-gnu)	17s
Docs (x86_64-unknown-illumos)	17s
Check (x86_64-unknown-linux-musl)	16s
Docs (x86_64-unknown-linux-gnu)	14s
Check (x86_64-unknown-netbsd)	14s
Docs (armv7-sony-vita-newlibeabihf)	28s
Docs (x86_64-unknown-linux-musl)	16s
Check (x86_64-unknown-redox)	15s
Docs (i686-unknown-hurd-gnu)	31s
Docs (x86_64-unknown-netbsd)	16s
Check (armv7-linux-androideabi)	16s
Docs (x86_64-unknown-redox)	16s
Check (i686-linux-android)	15s
Docs (armv7-linux-androideabi)	17s
Docs (i686-linux-android)	16s
	16m 39s

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