Debhelper 12 / Enable service with systemd

Currently, the packages do not enable the freeradius service by default on a fresh install on Buster or above.

The problem is due to a combination of the presence of a freeradius service file and the debhelper settings used to build the package:

• The packaging uses debhelper compat level 9.
• The systemd service file, freeradius.service was introduced for Stretch
• For debhelper compat levels up to 10, the service file is installed by dh_installinit, but the service is not enabled because the packaging invokes dh_installinit with the --noscripts flag

By moving to debhelper > 11, the packaging scripts end up using the new dh_installsystemd helper, which also enables the service by default.

I also had to extend the autogen process to generate all the configure files again, because the newer debhelper level passes the flag --runstatedir which is only in newer configure versions.