Update packaging to recent standards

This package has been stalled for almost 7 years by now. Update its packaging to fix existing Lintian issues, upgrade to policy 4.7.0 and use modern debhelper.

I marked this a non-maintainer upload, but I'd like to contact the maintainer soon, and see how he'd like to better deal with this package. Maybe this becomes a QA upload instead if the package is orphaned. If so, I'll rewrite the last commit to be consistent with this.