documentation enhanced

dune/curvedsurfacegrid/grid.hh

@@ -519,6 +519,8 @@ namespace Dune
 
     //! obtain constant reference to the coordinate function
     CoordFunction const& coordFunction () const { return *coordFunction_; }
+
+    //! obtain reference to the coordinate function
     CoordFunction& coordFunction () { return *coordFunction_; }
 
     bool useGeometryCaching () const