Fix delayed execution of X-Server events

Processing of the X-Server events could be delayed by up to 60 seconds.

If the X server message pump contains more than 20 events, the execution of this events is interrupted to check the state of active sockets.
The process stopps for up to 60 seconds, if no state changes on the sockets are detected.
The events in the X server queue are still waiting for execution at this time.