Add ability to pause/resume entire BitTorrent session

PR #20757.
Closes #18993.

src/base/bittorrent/torrentimpl.h

@@ -269,6 +269,7 @@ namespace BitTorrent
 
         void handleAlert(const lt::alert *a);
         void handleStateUpdate(const lt::torrent_status &nativeStatus);
+        void handleQueueingModeChanged();
         void handleCategoryOptionsChanged();
         void handleAppendExtensionToggled();
         void handleUnwantedFolderToggled();