[Rivet] Build of latest 2-6-x release branch

[David Yallup]

Hi All,

This is probably down to something I'm messing up but I was wondering if 
anyone has had any problems building the latest 2-6-x branch recently?

Specifically when I update to revision 6377 (current tip) I get a series 
of errors all pertaining to Rivet::Particles

In file included from ../../include/Rivet/AnalysisHandler.hh:6:0,
                  from Run.cc:3:
../../include/Rivet/Particle.hh: In constructor 
‘Rivet::Particle::Particle(const HepMC::GenParticle&)’:
../../include/Rivet/Particle.hh:53:32: error: no matching function for 
call to ‘Rivet::Particles::Particles()’
          _momentum(gp.momentum())


This is updating from revision 6250 (also on the 2-6-x branch) where 
everything built fine (which makes me think I'm doing something too 
stupid!). It looks like my compiler disagrees with the changes from

https://rivet.hepforge.org/hg/rivet/rev/5b2baf1011f6?revcount=120


If others have had no trouble with recent builds of rivet I will go back 
to the drawing board but thought I would check with others first.

Thanks,
David