Auto-sizing of single tab thumbnail ribbon, also on zoomin/out. Stops autosizing once you manually move the ribbon splitter.

rtgui/thumbbrowserbase.h

@@ -90,6 +90,7 @@ class ThumbBrowserBase  :  public Gtk::VBox {
 
     void zoomIn ()  { zoomChanged (true); }
     void zoomOut () { zoomChanged (false); }
+    int getEffectiveHeight ();
     
     const std::vector<ThumbBrowserEntryBase*>& getEntries () { return fd; }
     void styleChanged (const Glib::RefPtr<Gtk::Style>& style);