- Removed the restriction on using IPv6 address in IPv4 mode. This allow

- Removed the restriction on using IPv6 address in IPv4 mode.  This allow
  IPv4 options which contain IPv6 address to be specified.  For example
  the 6rd option can be specified and use like this:

        option 6rd code 212 = { integer 8, integer 8,
                                ip6-address, array of ip-address };
        option 6rd 16 10 2001:: 1.2.3.4, 5.6.7.8;