message: Fix fanout example build warnings on macOS
diff: extern crate pnet;
  extern crate pnet_datalink;
  -use pnet::datalink::{self, Config, FanoutOption, FanoutType, NetworkInterface};
  -use std::env;
  use std::io::{self, Write};
  use std::process;
  -use std::thread;
  #[cfg(not(target_os = "linux"))]
  fn main() {
  @@ -27,6 +24,9 @@ fn main() {
  #[cfg(target_os = "linux")]
  fn main() {
  use pnet::datalink::Channel::Ethernet;
  + use pnet::datalink::{self, Config, FanoutOption, FanoutType, NetworkInterface};
  + use std::env;
  + use std::thread;
  let iface_name = match env::args().nth(1) {
  Some(n) => n,
  