clean up genprod, get rid of warning  (#5361)
clean up genprod, get rid of warning  (#5361)

No more "Selecting value MAX_ARITY from object genprod, 
which extends scala.DelayedInit, is likely to yield an 
uninitialized value" at start of every build.
martijnhoekstra/scala,shimib/scala,martijnhoekstra/scala,slothspot/scala,slothspot/scala,slothspot/scala,lrytz/scala,shimib/scala,scala/scala,jvican/scala,jvican/scala,shimib/scala,lrytz/scala,scala/scala,jvican/scala,slothspot/scala,jvican/scala,felixmulder/scala,martijnhoekstra/scala,scala/scala,shimib/scala,felixmulder/scala,shimib/scala,felixmulder/scala,jvican/scala,jvican/scala,lrytz/scala,felixmulder/scala,jvican/scala,shimib/scala,slothspot/scala,lrytz/scala,slothspot/scala,felixmulder/scala,scala/scala,felixmulder/scala,lrytz/scala,scala/scala,martijnhoekstra/scala,martijnhoekstra/scala,slothspot/scala,scala/scala,martijnhoekstra/scala,felixmulder/scala,lrytz/scala