utils: Added sysfs netif readlink utility
iftypes: added s390 ctcm and iucv (slip) devices
iftypes: log link kind of unknown devices in debug2
ibft: fixed reading of the origin field
dhcp4: adjusted addrconf lease details

- Renamed serveraddress to server_id and fixed to not
  mix it with the boot-server-address (dhcp siaddr)
- Renamed servername to boot-server-name
- Added relay-address (dhcp giaddr) to the lease
- Use and opaque type for dhcp4 client-id
- Adjusted objectmodel transfer and leasefile/info
leaseinfo: consistently use prefixlen in ROUTES

Today the netmask is never used to set up something.
Consistently use prefixlen for ipv4 and ipv4 routes
so there is no need to relalculate for iproute2.