Ethernet.tick() - polling for active connection was too frequent

in UIP_CLIENT_TIMER mode (it is default) an active connection was polled
every tick()

Author: JAndrassy

src/Ethernet.cpp

@@ -256,7 +256,10 @@ UIPEthernetClass::tick()
       else
         {
           if (uip_conn->appstate != NULL && (long)( now - ((uip_userdata_t*)uip_conn->appstate)->timer) >= 0)
+            {
             uip_process(UIP_POLL_REQUEST);
+            ((uip_userdata_t*)uip_conn->appstate)->timer = millis() + UIP_CLIENT_TIMER;
+            }
           else
             continue;
         }