Qt4: Tell the window manager to keep the fullscreen controller window on top.

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
(cherry picked from commit 3311fb12660e8b3079526599d7fc14e830f5b09d)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/components/controller.cpp

@@ -650,7 +650,7 @@ FullscreenControllerWidget::FullscreenControllerWidget( intf_thread_t *_p_i, QWi
     vout.clear();
 
 #ifdef Q_WS_X11
-    setWindowFlags( Qt::Window | Qt::FramelessWindowHint );
+    setWindowFlags( Qt::Window | Qt::FramelessWindowHint | Qt::WindowStaysOnTopHint );
     setWindowModality( Qt::ApplicationModal );
 #else
     setWindowFlags( Qt::ToolTip );