Changes in musrPhysicsList.cc that were needed for new version of
Geant = Geant4.9.4. The changes remove G4MultipleScattering and
MultipleAndCoulombScattering, because multiple scattering has to
be treated differently for different particles in Geant4.9.4 and
"G4MultipleScattering" is not supported anymore. The documentation
has to be updated (i.e. comments about MultipleAndCoulombScattering
has to be removed from doc/musrSim.tex).