Don't optimise doxygen for C, when we are using C++. That "data structures" tab was annoying me.
Minimally rework main(), so that EventNavigator has control of the input file, and is the ultimate source of g_setup and g_data.  This eliminates the global gInFile.  Functions change as a result: TSetupData::Instance() is now just a wrapper;  GetTree() is eliminated; maybe some other stuff.