Fix for Iterator flattening regression.
Fix for Iterator flattening regression.

but my theory is that ++ takes a by name argument, but doing a foldLeft
and using ++ to join creates a closure which loses the by-nameness. If
this theory is correct that's an ugly trap.

Not sure how I write a test against this sort of thing? Will take
pointers. For now, closes #4582, no review.


shimib/scala,felixmulder/scala,martijnhoekstra/scala,jvican/scala,shimib/scala,jvican/scala,slothspot/scala,scala/scala,shimib/scala,jvican/scala,shimib/scala,scala/scala,martijnhoekstra/scala,lrytz/scala,jvican/scala,lrytz/scala,jvican/scala,slothspot/scala,shimib/scala,felixmulder/scala,martijnhoekstra/scala,lrytz/scala,scala/scala,felixmulder/scala,martijnhoekstra/scala,felixmulder/scala,shimib/scala,slothspot/scala,slothspot/scala,lrytz/scala,slothspot/scala,jvican/scala,slothspot/scala,lrytz/scala,scala/scala,felixmulder/scala,martijnhoekstra/scala,scala/scala,lrytz/scala,felixmulder/scala,martijnhoekstra/scala,jvican/scala,slothspot/scala,felixmulder/scala,scala/scala