make scripts/l10n/log-changes usable on non-po-debconf packages

[Robert Millan <rmh@aybabtu.com>]

Hi,

Without the help of scripts/l10n/output-l10n-changes it was becoming a PITA to
maintain changelog entries for translations in win32-loader, so I gave it a try
and discovered scripts/l10n/log-changes had some bits specific to po-debconf
packages.

This patch makes scripts/l10n/log-changes usable on non-po-debconf packages.
I don't think it breaks anything, but then again can't be sure of it since I
know very little about D-I l10n infrastructure.

Is it ok for commit?

-- 
Robert Millan

<GPLv2> I know my rights; I want my phone call!
<DRM> What use is a phone call, if you are unable to speak?
(as seen on /.)