372: Implement Eq and Hash for socket2::SockAddr

[lshlyapnikov]

Closes: #372.

This PR started as: #373, which was based off of v0.4.x by mistake, changing the base to master.

Cannot derive Eq and Hash for socket2::SockAddr because sockaddr_storage does not have both traits derived/implemented. sockaddr_storage is defined within s_no_extra_traits, my assumption it is expected to stay this way and I should not derive/implement Eq and Hash for sockaddr_storage.

TODO:

• add test cases. Quickcheck tests removed from this PR, can be found here: https://github.com/lshlyapnikov/socket2/blob/sockaddr-quickcheck/src/sockaddr.rs#L501-L554
• add benchmarks for socket2::SockAddr::as_socket + std::net::SocketAddr::hash vs socket2::SockAddr::hash (this implementation). Benchmarks are not part of this PR, can be found here: https://github.com/lshlyapnikov/socket2/blob/sockaddr-quickcheck/benches/sockaddr_bench.rs

[lshlyapnikov]

Benchmarks socket2::SockAddr::hash vs socket2::SockAddr::as_socket + std::net::SocketAddr::hash

https://github.com/lshlyapnikov/socket2/blob/sockaddr-quickcheck/benches/sockaddr_bench.rs

    bench.iter(|| {
        x.hash(&mut hasher);
        hasher.finish()
    })

    bench.iter(|| {
        x.as_socket().map(|y| y.hash(&mut hasher));
        hasher.finish()
    })

$ cargo bench
...
Running benches/sockaddr_bench.rs (target/release/deps/sockaddr_bench-8434022fa4125c76)

running 2 tests
test benchmark_as_socket_hash ... bench:          42 ns/iter (+/- 21)
test benchmark_hash           ... bench:          19 ns/iter (+/- 8)

I will keep these benchmarks in my fork. Let me know when/if you want to add them to the master.

[Thomasdezeeuw]

Running benches/sockaddr_bench.rs (target/release/deps/sockaddr_bench-8434022fa4125c76)

running 2 tests
test benchmark_as_socket_hash ... bench: 42 ns/iter (+/- 21)
test benchmark_hash ... bench: 19 ns/iter (+/- 8)

Looks pretty decent.

I will keep these benchmarks in my fork. Let me know when/if you want to add them to the master.

I think that's ok for now. If we ever get a complaint about the performance we can add them.

Thanks for the pr.