G4ExternalDecay: thread-checker fixes
Cleanup the Pythia8ForDecays singleton (no need for complicated mutex
logic, static initialization is thread-safe) and mark is as not
thread-safe because it exposes a non-const pointer to a static.
Cleanup the Pythia8ForDecays singleton (no need for complicated mutex
logic, static initialization is thread-safe) and mark is as not
thread-safe because it exposes a non-const pointer to a static.