sci-physics/root: update pythia dependency

Since pythia-8.1.80 API was changed and <root-5.34.11 supports only
lower pythia verions. This fixes bug 490332.
sci-chemistry/freeon-1.0.8: Version bump.

Package-Manager: portage-2.2.7
sci-physics/root: update dependencies and eclass

- Update pythia8 dependency.
- Use EAPI=5.
- Migration to python-single-r1 eclass.
Merge remote-tracking branch 'github/master'

* github/master:
  sci-physics/thepeg: USE flags fixed for ver. 1.9.0
  sci-physics/LoopTools: ~amd64 keyword added, EAPI=5