Socket into/from/as

test.rs

  let family: c_int = 2;
  let ty: c_int = 1;
  let proto: c_int = 6;

  let raw_socket;

  {
      let socket = Socket::new(family, ty, proto).unwrap();
      raw_socket = socket.into_raw_socket();
  }

  let socket = unsafe { Socket::from_raw_socket(raw_socket) };

  assert_eq!(raw_socket, socket.as_raw_socket());
  assert!(socket.close().is_ok());