TGeoManager and TGeoMatrix as declarations only.

core/base/utils/CbmGeometryUtils.h

@@ -3,10 +3,11 @@
    Authors: Florian Uhlig [committer], Eoin Clerkin */
 
 #include "Rtypes.h"
-#include "TGeoManager.h"
 
 class TGeoMatrix;
 class TGeoVolume;
+class TGeoManager;
+class TGeoMedium;
 class FairModule;
 class TString;