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).