Proposed changes to aut-num policy syntax in RPSLng

    Andrei Robachevsky has proposed the following changes
to the syntax for policy expressions in RPSLng based on
feedback from the list and a desire to simplify the syntax for
the case where v4/v6 and/or unicast/multicast policy are converged.

1)  the absence of safi in an expression means that both
    unicast and multicast are defined.  I.e.,

  afi ipv4 == afi ipv4.unicast,ipv4.multicast

2)  The afi specification will be optional in the mp-*
   attributes in the aut-num class.  If no afi is
   specified, the policy shall be expanded to include
   all afi and safi types, namely --

  afi ipv4.unicast,ipv4.multicast,ipv6.unicast,ipv6.multicast

3)  introduce a pseudo afi with the value of "any".  I.e., 

  afi any.unicast == afi ipv4.unicast,ipv6.unicast
  afi any == afi ipv4.unicast,ipv6.unicast,ipv4.multicast,ipv6.multicast


    Looking forward to your feedback.

 Regards,
   Larry