PyQGIS: fixed invalid signature of writeXML function

git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@11407 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: wonder

python/core/qgsgraduatedsymbolrenderer.sip

@@ -65,7 +65,7 @@ class QgsGraduatedSymbolRenderer : QgsRenderer
 
     /**Writes the contents of the renderer to a configuration file
      @ return true in case of success*/
-    virtual bool writeXML( QDomNode & layer_node, QDomDocument & document, QgsVectorLayer& vl ) const;
+    virtual bool writeXML( QDomNode & layer_node, QDomDocument & document, const QgsVectorLayer& vl ) const;
 
     /** Returns true*/
     bool needsAttributes() const;