[PATCH] IPA: fix reproducibility in IPA MOD REF

[Jan Hubicka]

> > > 
> > > Isn't problem that the following code
> > > 
> > >                past_flags.reserve_exact (summary->arg_flags.length ());
> > >                past_flags.splice (summary->arg_flags);
> > >                past_retslot_flags = summary->retslot_flags;
> > 
> > Aha, that makes sense. Sorry.  It used to be saved for dumping only
> > while we now use it to merge old summaries with new.  So it is indeed a
> > (quite stupid) bug.
> 
> Good :) Good. I thought I overlooked something.
Hehe, I overlooked a hunk while breaking the patches into more
independent changes.

I planed a cleanup of this code after pushing out the new features.
Pehraps a trivial parts of the cleanup can be done even in stage3.
Honza