Update GenEvent_p6 so that the classes match in HepMC2 and HepMC3.
The persistent McEventCollection_p6
format should be the same in HepMC2-based and HepMC3-based releases. This MR tweaks the GenEvent_p6
class so that the m_filterWeight
member variable exists in HepMC2-based releases also, but is just set to its default value during T->P conversion and is not used during P->T conversion.
Part of the work for ATLINFR-4725.