Merge branch 'clang.GenInterfaces-20201118' into 'master'

GenInterfaces+TrackCaloClusterRecInterfaces: Fix clang warnings.

See merge request atlas/athena!38370

Generators/GenInterfaces/GenInterfaces/IHiggsTruthCategoryTool.h

@@ -15,7 +15,7 @@
 #include "HepMC/GenEvent.h"
 
 namespace HTXS {
-  class HiggsClassification;
+  struct HiggsClassification;
 }
 
 class IHiggsTruthCategoryTool : public virtual asg::IAsgTool {

Reconstruction/TrackCaloClusterRec/TrackCaloClusterRecInterfaces/TrackCaloClusterRecInterfaces/ITrackCaloClusterTool.h

@@ -16,7 +16,7 @@
 static const InterfaceID IID_ITrackCaloClusterTool("ITrackCaloClusterTool", 1, 0);
 
 
-class TrackCaloClusterInfo;
+struct TrackCaloClusterInfo;
 
 /** @brief Interface for tools creating particles using TCC methods and filling a FlowElementContainer */
 class ITrackCaloClusterTool : virtual public IAlgTool {