[d-i] Ubuntu-related strings in apt-setup

[Colin Watson <cjwatson@debian.org>]

Per http://lists.debian.org/debian-boot/2005/10/msg01407.html and
followups, I've arranged for strings for apt-setup's Ubuntu mirror
generator to be added to the d-i translation master files at the next
update. They're not too different from the normal strings, and I made
sure to put translator comments in the additional templates to say that
they're only used in a derived distribution.

Christian Perrier and Frans Pop suggested that I post a short message to
-i18n to explain the situation, hence this mail.

Thanks,

-- 
Colin Watson                                       [cjwatson@debian.org]