libdatetime-timezone-perl: timezone updates in stable

[Ansgar Burchardt <ansgar@debian.org>]

Hi,

from <https://bugs.launchpad.net/bugs/724044>:
> Binary package hint: libdatetime-timezone-perl
>
> This package provides TimeZone information to Perl programs using the
> DateTime module.  So this module should be updated with the same
> policy as the 'tzdata' package, which means being volatile. See
> http://www.debian.org/volatile/
>
> See this message on the DateTime mailing list as a reference:
> http://marc.info/?l=perl-datetime&m=129848974132157&w=2

Judging from libdatetime-timezone-perl's debian/README.NMU it looks
possible to just refresh the timezone database without changing the rest
of the package.

Should we try to keep this at least not behind tzdata in stable?

Ansgar