synchronize distro/deb with official debian packaging

Note that this is not an exact synchronization, just the salient parts where i believe upstream wants to sync up with debian.

I've left alone indications of upstream package maintainership, and I've left debhelper back at version 9, for example. and i've left the differences between the shipped debian/kresd.conf (debian package ships a minimal kresd.conf that doesn't load those four modules, in particular).