Add factory annotation

Author: mhugent

python/core/geometry/qgsgeometry.sip

@@ -682,7 +682,7 @@ class QgsGeometry
     QgsPolyline smoothLine( const QgsPolyline &polyline, const unsigned int iterations = 1, const double offset = 0.25 ) const;
 
     /** Creates and returns a new geometry engine*/
-    static QgsGeometryEngine* createGeometryEngine( const QgsAbstractGeometryV2* geometry );
+    static QgsGeometryEngine* createGeometryEngine( const QgsAbstractGeometryV2* geometry ) /Factory/;
 
 }; // class QgsGeometry