[Rivet] HepMC static

[James Monk]

Hi Riveteers,

The version of HepMC that we are distributing at Cedar only builds a  
static library on OS X, which is obviously going to cause some  
problems for RivetGun dynamic loading.  I've modified the HepMC build  
script to make a dynamic library as well and everything seems to be  
fine (once again, only OS X >= v3). I'll put that version of HepMC in  
the Cedar downloads area (still the same version 2.02.00), which you  
will need to install if you want to run Rivet on OS X (is anyone else  
using it?).  Nothing changes on Linux, obviously.  Should I notify  
the HepMC developers that they need to make this change in all future  
releases, or do we make the release anyway?

I also found out that the  libAGILe*Mod.so files that RivetGun builds  
are not useful (get a bus error when trying to dlopen them).  The  
solution to this was to build them as dylibs like everything else by  
removing the -module linker flag and then they seem to work.  I'll  
commit a change for this shortly and hopefully that will be the end  
of this .dylib/.so saga.

cheers,

James