support channel up and channel down remote keys QT4+win32

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/main_interface_win32.cpp

@@ -194,9 +194,11 @@ bool MainInterface::winEvent ( MSG * msg, long * result )
                 case APPCOMMAND_MEDIA_PAUSE:
                     THEMIM->pause();
                     break;
+                case APPCOMMAND_MEDIA_CHANNEL_DOWN:
                 case APPCOMMAND_MEDIA_PREVIOUSTRACK:
                     THEMIM->prev();
                     break;
+                case APPCOMMAND_MEDIA_CHANNEL_UP:
                 case APPCOMMAND_MEDIA_NEXTTRACK:
                     THEMIM->next();
                     break;