Merge branch 'hepmc3_in_atlashepmc' into 'master'

Generators/AtlasHepMC/AtlasHepMC/GenEvent.h

Generators/AtlasHepMC/AtlasHepMC/GenEvent_fwd.h

Generators/AtlasHepMC/AtlasHepMC/GenParticle.h

Generators/AtlasHepMC/AtlasHepMC/GenParticle_fwd.h

Generators/AtlasHepMC/AtlasHepMC/GenRanges.h

Generators/AtlasHepMC/AtlasHepMC/GenVertex.h

Generators/AtlasHepMC/AtlasHepMC/GenVertex_fwd.h

Generators/AtlasHepMC/AtlasHepMC/HEPEVT_Wrapper.h

Generators/AtlasHepMC/AtlasHepMC/HeavyIon.h

Generators/AtlasHepMC/AtlasHepMC/IO_AsciiParticles.h

Generators/AtlasHepMC/AtlasHepMC/IO_BaseClass.h

Generators/AtlasHepMC/AtlasHepMC/IO_GenEvent.h

Generators/AtlasHepMC/AtlasHepMC/IO_HEPEVT.h

Generators/AtlasHepMC/AtlasHepMC/IO_HERWIG.h

Generators/AtlasHepMC/AtlasHepMC/PdfInfo.h

Generators/AtlasHepMC/AtlasHepMC/Polarization.h

Generators/AtlasHepMC/AtlasHepMC/SimpleVector.h

Generators/AtlasHepMC/AtlasHepMC/WeightContainer.h

Generators/AtlasHepMC/CMakeLists.txt