* Add a new build option 'firewalld-zone'; when enabled, NetworkManager installs a firewalld zone for connection sharing and puts interfaces using IPv4 or IPv6 shared mode in this zone during activation. The option is enabled by default. Note that NetworkManager still calls to iptables to enable masquerading and open needed ports for DHCP and DNS. The new option is useful on systems using firewalld with the nftables backend, where the iptables rules would not be sufficient.