Increase videowidget size priority over the others.

At the moment it is redumbdant with 6ec764ae
(QSizePolicy::Expanding) but it will be needed when the docked playlist
is re-implemented

modules/gui/qt4/main_interface.cpp

@@ -436,7 +436,7 @@ void MainInterface::handleMainUi( QSettings *settings )
     if( videoEmbeddedFlag )
     {
         videoWidget = new VideoWidget( p_intf );
-        mainLayout->insertWidget( 0, videoWidget );
+        mainLayout->insertWidget( 0, videoWidget, 10 );
 
         var_Create( p_intf, "window_widget", VLC_VAR_ADDRESS );
         vlc_value_t val;