TruthUtils → AtlasHepMC Relation

File in Generators/TruthUtils/TruthUtils	Includes file in Generators/AtlasHepMC
MagicNumbers.h	AtlasHepMC / GenEvent.h
MagicNumbers.h	AtlasHepMC / GenParticle.h
MagicNumbers.h	AtlasHepMC / GenVertex.h