gcc12 changed the things, again

Let debhelper manage those

i2c-tools is restricted to these architectures

Override systemd-service-file-refers-to-unusual-wantedby-target for nut-client and nut-server packages

Update to upstream version '2.8.0'
with Debian dir e9ae7053be63c3bfab1f0168722657e511d62f4c

Dynamic exception specifications are obsolete and g++-11 throws errors
when it find them.  Upstream has removed them.  This commit adds the
upstream patch, rebased to apply against the source of the Debian
pacakge.

Fix some issues reported by lintian

See merge request !1