add illumos support

src/udp.rs

@@ -20,10 +20,11 @@ fn new_socket(addr: SocketAddr, reuse: bool, buf_size: usize) -> Result<Socket,
         SocketAddr::V6(..) => Socket::new(Domain::ipv6(), Type::dgram(), None),
     }?;
     if reuse {
-        // windows has no reuse_port, but it's reuse_address
+        // windows has no reuse_port, but its reuse_address
         // almost equals to unix's reuse_port + reuse_address,
         // though may introduce nondeterministic behavior
-        #[cfg(unix)]
+        // illumos has no support for SO_REUSEPORT
+        #[cfg(all(unix, not(target_os = "illumos")))]
         socket.set_reuse_port(true).ok();
         socket.set_reuse_address(true).ok();
     }