Emit statuschange in qt4-interface when video-es change (track-count changes)

this should fix #1778, because with ts-files you don't allways have info about
video-tracks when input is started (and qt4 interface only called
controls->updateInput when status changed).

I didn't create new callback/signal for this one, but it could be cleaner that way.

modules/gui/qt4/input_manager.cpp

@@ -141,6 +141,9 @@ void InputManager::addCallbacks()
     var_AddCallback( p_input, "state", ItemStateChanged, this );
     /* src/input/es-out.c:552 */
     var_AddCallback( p_input, "spu-es", ChangeSPU, this );
+    /* emit UpdateStatus so that main_interface updates controls 
+     * if there is new videotracks (mpeg-ts)*/
+    var_AddCallback( p_input, "video-es", ItemStateChanged, this );
     /* src/input/es-out.c: */
     var_AddCallback( p_input, "teletext-es", ChangeTeletext, this );
     /* src/input/input.c:1765 */
@@ -155,6 +158,7 @@ void InputManager::addCallbacks()
 void InputManager::delCallbacks()
 {
     var_DelCallback( p_input, "spu-es", ChangeSPU, this );
+    var_DelCallback( p_input, "video-es", ItemStateChanged, this );
     var_DelCallback( p_input, "teletext-es", ChangeTeletext, this );
     var_DelCallback( p_input, "state", ItemStateChanged, this );
     var_DelCallback( p_input, "rate-change", ItemRateChanged, this );