Add GeoOpticalPhysVol to GeoMaterial2G4, they should be needed later

GeoMaterial2G4/GeoMaterial2G4/GeoOpticalPhysVol.h

+/*
+  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+*/
+
+#ifndef GeoOpticalPhysVol_h
+#define GeoOpticalPhysVol_h 1
+
+#include "GeoModelKernel/GeoPhysVol.h"
+
+class GeoOpticalPhysVol : public GeoPhysVol
+{
+ public:
+  GeoOpticalPhysVol(const GeoLogVol* LogVol);
+
+ protected:
+  ~GeoOpticalPhysVol();
+
+ private:
+  GeoOpticalPhysVol(const GeoOpticalPhysVol &right);
+  GeoOpticalPhysVol & operator=(const GeoOpticalPhysVol &right);
+
+};
+
+#endif 
+

GeoMaterial2G4/src/GeoOpticalPhysVol.cxx

+*
+  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+*/
+
+#include "GeoModelUtilities/GeoOpticalPhysVol.h"
+
+GeoOpticalPhysVol::GeoOpticalPhysVol(const GeoLogVol* LogVol):
+  GeoPhysVol(LogVol)
+{
+}
+
+GeoOpticalPhysVol::~GeoOpticalPhysVol()
+{
+}
+