Modified starlight to compile under AppleClang 7.3.0.7030031 without compilation errors.
This involved:

adding getMass and setMass to starlightparticle.h

removing _sigmaSum from gammagammasingle.h & gammagammaleptonpair.h

removing private members from starlight.h/starlight.cpp

initialized theta =0. in gammagammaleptonpair.cpp, if you see your pairs with an invalid spin going in the z-dir, this is probably why.

removed ntracks from upcevent

made operator<< to match the other inline friends of operator<<.