IO: Avoid multiple event cycles in one loop cycle.

Event cycle may took too much time and trigger next timer events, so
avoid cycling between timer and event cycles inside the loop cycle.

sysdep/unix/io.c

@@ -2055,12 +2055,13 @@ io_loop(void)
   for(;;)
     {
       events = ev_run_list(&global_event_list);
+    timers:
       update_times();
       tout = tm_first_shot();
       if (tout <= now)
 	{
 	  tm_shot();
-	  continue;
+	  goto timers;
 	}
       poll_tout = (events ? 0 : MIN(tout - now, 3)) * 1000; /* Time in milliseconds */