[RF] Exclude RooHistError from IO

This singleton helper class should not be serializable.

roofit/roofitcore/inc/LinkDef.h

@@ -124,7 +124,6 @@
 #pragma link C++ class RooGenContext+ ;
 #pragma link C++ class RooGenericPdf+ ;
 #pragma link C++ class RooGenProdProj+ ;
-#pragma link C++ class RooHistError+ ;
 #pragma link C++ class RooHist+ ;
 #pragma link C++ class RooImproperIntegrator1D+ ;
 #pragma link C++ class RooIntegrator1D+ ;

roofit/roofitcore/inc/RooHistError.h

@@ -131,7 +131,6 @@ private:
     Int_t _N1 ;
   } ;
 
-  ClassDef(RooHistError,1) // Utility class for calculating histogram errors
 };
 
 #endif

roofit/roofitcore/src/RooHistError.cxx

@@ -34,10 +34,6 @@ a specified area of a Poisson or Binomail error distribution.
 
 using namespace std;
 
-ClassImp(RooHistError);
-  ;
-
-
 
 ////////////////////////////////////////////////////////////////////////////////
 /// Return a reference to a singleton object that is created the