Well this has wound up a little more ‘touch all the files’ than planned,
turns out intl.h was included in some headers somewhat exploding the
places gi18n needed to be included…

Anyway, this should avoid some unexpected weirdness with includes and
gettext working right.

Hopefully we can drop intl.{c,h} entirely, this scoring thing seems a
tad iffy, but at least for now we've cut it down.