Remove debian packaging scripts

This removes the debian directory which used to contain packaging scripts.

Each debian/ubuntu version needs slightly different scripts, so having this
upstream wasn't that helpful.

If you want to create your own debian packages, then you can use some of
the existing packaging scripts as a template. E.g. the debian upstream scripts at
URL: http://anonscm.debian.org/git/pkg-grass/osm2pgsql.git
or, a set of scripts used to build Ubuntu PPAs:
https://github.com/apmon/OSM-rendering-stack-deplou/tree/master/launchpad