Calling Xsync from the bg thread causes deadlock issues

diff -up allegro-4.4.2/src/x/xwin.c~ allegro-4.4.2/src/x/xwin.c

--- allegro-4.4.2/src/x/xwin.c~	2009-10-17 09:05:12.000000000 +0200

+++ allegro-4.4.2/src/x/xwin.c	2014-10-29 15:17:08.381148654 +0100

@@ -2463,11 +2463,8 @@ void _xwin_private_handle_input(void)

 		   _mouse_y - (_xwin_mouse_extended_range ? _xwin.scroll_y : 0));

    }

-   /* Flush X-buffers.  */

-   _xwin_private_flush_buffers();

-

    /* How much events are available in the queue.  */

-   events = events_queued = XEventsQueued(_xwin.display, QueuedAlready);

+   events = events_queued = XPending(_xwin.display);

    if (events <= 0)

       return;