Implement I/O safety traits #485

Job	Run time
Docs	19s
Clippy	12s
Check (aarch64-apple-ios)	33s
CheckTargets	1m 26s
Check (aarch64-apple-tvos)	32s
MinimalVersions (ubuntu-latest)	18s
Check (aarch64-unknown-openbsd)	33s
MinimalVersions (macos-latest)	29s
Check (arm64_32-apple-watchos)	29s
MSRV (ubuntu-latest)	11s
Nightly	21s
MinimalVersions (windows-latest)	38s
Check (armv7-sony-vita-newlibeabihf)	29s
MSRV (macos-latest)	17s
Check (sparcv9-sun-solaris)	28s
MSRV (windows-latest)	42s
Check (x86_64-pc-solaris)	29s
Rustfmt	4s
Sanitizer (address)	47s
Check (x86_64-unknown-dragonfly)	32s
Sanitizer (leak)	40s
Check (x86_64-unknown-openbsd)	30s
Sanitizer (memory)	1m 7s
Test (ubuntu-latest)	40s
TestPoll	39s
Test (macos-latest)	1m 2s
Sanitizer (thread)	43s
Test (windows-latest)	2m 22s
TestWakerPipe	38s
Passed	1s
	18m 11s

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