gzip: enable for IPRO as well & style fixes

2 commits:
c08ac0eebf9c4f50bcdd9c775a67f2bd0cc3da0c: style fixes (and a few notes)
c7685059903d1ce1ef25c4baf4eaaac8c05f3693: also enable gzip when IPRO is on

@keesspoelstra please have a good look at both commits. a few notes need addressing
(see) "@keesspoelstra" and after that I think this is set.