some functions were missing after "cleanups" of Andreas

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@7602 2fb0f335-1f38-0410-981e-8018bf24f1b0

dumux/material/components/xylene.hh

@@ -236,7 +236,7 @@ public:
      */
     static Scalar liquidDensity(Scalar temperature, Scalar pressure)
     {
-        return (molarLiquidDensity(temperature, pressure)*molarMass()); // [kg/m^3]
+        return molarLiquidDensity(temperature, pressure)*molarMass(); // [kg/m^3]
     }
 
     /*!