Check for a translation Language-Team pointing to debian-i18n

* checks/po-debconf{,.desc}:
  + [RA] Add new check for a Language-Team field in a translation
    pointing to the debian-i18n mailing list.  Based on work by
    victory.  (Closes: #705197)
Remove some left-over po-debconf language team code

Forgot to clean up some left-over variables after my original
attempt.
Clean up more unneeded code in po-debconf check
Add =encoding to the POD in Lintian::Collect

We use a UTF-8 section symbol, and the current version of Pod::Simple
therefore requires explicitly declaring the character set.
lib+t: Convert a couple of modules to use autodie

Signed-off-by: Niels Thykier <niels@thykier.net>