* Introduce a new "link" setting that holds properties related to the
  kernel link such as "tx-queue-length", "gso-max-size",
  "gso-max-segments", "gro-max-size".
* Support sending a DHCPv6 prefix delegation hint via the
  "ipv6.dhcp-pd-hint" connection property.
* Support new bond options: "arp_missed_max", "lacp_active",
  "ns_ip6_target".
* Add new "initial-eps-bearer-configure" and "initial-eps-bearer-apn"
  properties in the GSM setting.