Fix the X11 build error

This makes qtmultimedia build again by moving down X11 includes.
See http://lists.qt-project.org/pipermail/development/2013-September/012986.html

Change-Id: If6cd5e80c27de7aaa8d2a65ded05500ed9d0e692
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Laszlo Papp <lpapp@kde.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>

src/multimedia/gsttools_headers/qgstxvimagebuffer_p.h

@@ -59,6 +59,9 @@
 #include <QtCore/qwaitcondition.h>
 #include <QtCore/qqueue.h>
 
+#include <gst/gst.h>
+#include "qgstbufferpoolinterface_p.h"
+
 #include <X11/Xlib.h>
 #include <sys/ipc.h>
 #include <sys/shm.h>
@@ -67,9 +70,6 @@
 #include <X11/extensions/Xv.h>
 #include <X11/extensions/Xvlib.h>
 
-#include <gst/gst.h>
-#include "qgstbufferpoolinterface_p.h"
-
 QT_BEGIN_NAMESPACE
 
 class QGstXvImageBufferPool;