Nuttx work with tokio net features

[wllenyj]

Description

Currently the nuttx rust app is not compiled, when using the tokio net feature.
Therefore, added support Nuttx definitions.

Sources

Added strerror_r function for errno crate. And errno crate 's pr lambda-fairy/rust-errno#129.
Added socket interrelated structs, functions and constants.
Added netinet interrelated structs and constants.
Added eventfd definitions, and poll/fcntl/tcp/pipe2 definitions.

Other interrelated pr rust-lang/socket2#663, tokio-rs/mio#1966, tokio-rs/tokio#8259.

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI