add Geant namespace

src/Math/CLHEP_defs.hh

@@ -1,6 +1,9 @@
+#if !defined(HAVE_GEANT4) && !defined(HEP_SYSTEM_OF_UNITS_H) && !defined(HEP_PHYSICAL_CONSTANTS_H)
 #ifndef CLHEP_defs_h
 #define CLHEP_defs_h
 
+
+
 namespace CLHEP {
 
 
@@ -365,4 +368,6 @@ static constexpr double universe_mean_density = 1.e-25*g/cm3;
 
 }  // namespace CLHEP
 
-#endif
+#endif // CLHEP_defs_h
+#endif // HAVE_GEANT4 / CLHEP checks
+