asiolink: fix build with boost 1.66

- use native_handle() for getting native socket type
- use io_context instead of io_service

src/lib/asiolink/udp_socket.h

@@ -61,7 +61,11 @@ public:
 
     /// \brief Return file descriptor of underlying socket
     virtual int getNative() const {
+#if BOOST_VERSION < 106600
         return (socket_.native());
+#else
+        return (socket_.native_handle());
+#endif
     }
 
     /// \brief Return protocol of socket