Various bugfix:

- pipette buttons are now mutually exclusive
- pipette from L curve (Lab tool) now works properly
- pipette from B curve (RGB tool) now works properly
- curve that doesn't handle the pipette mechanism hides the pipette button
- RGB components of the Tone Curves' pipette now displayed in red, green & blue
- the vertical line where the point will be inserted is displayed in grey and has a line's width of 2 pixels

rtgui/imagearea.h

@@ -122,6 +122,7 @@ class ImageArea : public Gtk::DrawingArea, public CropWindowListener, public Edi
     // EditDataProvider interface
     void subscribe(EditSubscriber *subscriber);
     void unsubscribe();
+    void getImageSize (int &w, int&h);
 
     // CropWindowListener interface
     void cropPositionChanged   (CropWindow* cw);