[Rivet] FHerwig in Agile

[Gavin Hesketh]

Hello,
I noticed a problem when trying to run Herwig without hadronisation. It 
seems the soft underlying event has to be turned off also, otherwise 
Herwig is never able to produce events.

ie:

       if (_doHadronise) {
         FC_HWCFOR();  // Do cluster formation
         FC_HWCDEC();  // Do cluster decays
         FC_HWDHAD();  // Do unstable particle decays
         FC_HWDHVY();  // Do heavy flavor decays
       }

       FC_HWMEVT();  // Add soft underlying event
       FC_HWUFNE();  // Finish event
       if (FC_HWEVNT.IERROR == 0) break;


the call to FC_HWMEVT() needs to be moved into the _doHadronise 
conditional in order to get any events.

This is an empirical observation, I don't really understand what happens...

FHerwig.cc and FHerwigJimmy.cc both need to be updated.

cheers,
	Gavin