The point of this package is to prompt the user who's installing Debian to
get their timezone. We base the prompt on the country they told the
installer they were in. 

Most countries have only one timezone, and for those the country-zone
mapping is stored in the tzmap file (automatically generated from
zone.tab), and no question is asked. Some countries have multiple timezones
listed in zone.tab, but these are only of historical interest (ie, to get
the correct time at some point in the past), and are thus not worth
bothering the user about during install. For these the tzmap.override file
can be used to force a whole country to one zone.

The remaining countries, those with more than one current timezone, have
questions listing the zones. The build process will look for these and try
to generate appropriate debconf templates, but as the data in zone.tab is
not very user-friendly, manual modification is needed in almost all cases.
For example, in the US, manual modification is used to pick a half-way good
default time zone, and to list the most common zones first using the common
names for the zones. So we have a manually edited
debian/common.templates.in, which is processed and any missing questions
added, to generate debian/common.templates.

The appropriate template is registered to the time/zone question at
runtime, so only that one question is ever asked.

Another tricky bit is translation. Currently the C values in the templates
are the raw timezone names. We use an English translation, which changes
these to more human readable zone names or place names. Translators have to
follow along, translating the C values into something that is appropriate
in their languages.

This does mean that this package will need the occasional update as
timezones change, as it's not all pulled directly from the zoneinfo.