speed up un-cached directories

embedded thumbnails will be used for the first pass when cached thumbnails are not found.

rtgui/thumbbrowserbase.h

@@ -95,6 +95,7 @@ class ThumbBrowserBase  :  public Gtk::VBox {
     void styleChanged (const Glib::RefPtr<Gtk::Style>& style);
     void redraw ();   // arrange files and draw area
     void refreshThumbImages (); // refresh thumbnail sizes, re-generate thumbnail images, arrange and draw
+    void refreshQuickThumbImages (); // refresh thumbnail sizes, re-generate thumbnail images, arrange and draw
     void refreshEditedState (const std::set<Glib::ustring>& efiles);
      
     void initEntry (ThumbBrowserEntryBase* entry);