Fix a small layout issue

Please see these captures
http://people.via.ecp.fr/~jpeg/VideoLAN/captures/capture15.png (buggy)
http://people.via.ecp.fr/~jpeg/VideoLAN/captures/capture14.png (no bug)

modules/gui/qt4/components/interface_widgets.cpp

@@ -280,6 +280,7 @@ AdvControlsWidget::AdvControlsWidget( intf_thread_t *_p_i ) :
     QHBoxLayout *advLayout = new QHBoxLayout( this );
     advLayout->setMargin( 0 );
     advLayout->setSpacing( 0 );
+    advLayout->setAlignment( Qt::AlignBottom );
 
     /* A to B Button */
     ABButton = new QPushButton( "AB" );