FEATURE: User can set alternative speed limits for fast toggling

Bandwidth scheduler is not functional yet (but appears in program preferences)

src/GUI.h

@@ -143,6 +143,7 @@ public slots:
   void setTabText(int index, QString text) const;
   void showNotificationBaloon(QString title, QString msg) const;
   void downloadFromURLList(const QStringList& urls);
+  void updateAltSpeedsBtn(bool alternative);
 
 protected:
   void closeEvent(QCloseEvent *);