Add a makefile for building debian packages This allow building debian source package from sdist. This is cleaner than building from hg clone because we ensure to only include what's listed in sdist MANIFEST.in in upstream tarball. The deb-zip target allow to build a zip for the source package, suitable as input of https://jenkins.intra.logilab.fr/job/pkg-from-dsc The deb target build the binary packages using sbuild.