[Rivet] Rivet plotting

[Jeppe R. Andersen]

Hello Hendrik and Rivets,

> Nope, it's not. Looks more like a missing pstricks. I thought we ship
> all those files with Rivet. Are you using the rivetenv.sh script?

pstricks is already included in texlive, but I also used
'source /home/andersen/Build/Rivet-1.8.2/rivetenv.csh' in my tcsh, and
'sh /blah/.../rivetenv.sh' in a trial bash, but still got the same
problem.

Cheers, Jeppe