Added/Implemented GtkCellSizeRequestIface

This patch adds height-for-width geometry management
for cell renderers while still responding to the old
gtk_cell_renderer_get_size() apis with virtual return values
(obtained by soliciting the new height-for-width cell renderer
apis).

gtk/gtkcellrenderer.h

@@ -174,6 +174,14 @@ void             gtk_cell_renderer_stop_editing   (GtkCellRenderer      *cell,
                                                    gboolean              canceled);
 
 
+void            _gtk_cell_renderer_calc_offset    (GtkCellRenderer      *cell,
+						   const GdkRectangle   *cell_area,
+						   GtkTextDirection      direction,
+						   gint                  width,
+						   gint                  height,
+						   gint                 *x_offset,
+						   gint                 *y_offset);
+
 G_END_DECLS
 
 #endif /* __GTK_CELL_RENDERER_H__ */