ipa-pure-const fixes

[Jan Hubicka]

> > I am testing the following patch.  It also makes the code merging
> > previously known to merge in looping flag when we think function is NEITHER
> > but we previously knew more.
> > I don't think this can change results since we don't have user attribute
> > for looping pure, but it is better to be safe then sorry.
> 
> Thanks, I'll test it once installed and report the result.

OK, comitted now.
Thanks!
Honza