Hepmc3 nightly fixes 04122020 part 7
In this MR:
- Make xAODHepMCtool compatible with HePMC3
This MR contains also !38878 (merged) Therefore either 38878 should be merged before this MR, or this MR should be merged alone.
In this MR:
This MR contains also !38878 (merged) Therefore either 38878 should be merged before this MR, or this MR should be merged alone.