dnsmasq: support hostid ipv6 address suffix option

dnsmasq: support hostid ipv6 address suffix option

Add support for hostid dhcp config entry to dnsmasq. This allows
specification of dhcpv6 hostid suffix and works in the same way as
odhcpd.

Entries in auto generated dnsmasq.conf should conform to:

dhcp-host=mm:mm:mm:mm:mm:mm,IPv4addr,[::V6su:ffix],hostname

example based on sample config/dhcp entry:

config host
        option name 'Kermit'
        option mac 'E0:3F:49:A1:D4:AA'
        option ip '192.168.235.4'
        option hostid '4'

dhcp-host=E0:3F:49:A1:D4:AA,192.168.235.4,[::0:4],Kermit

Signed-off-by: Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk>