Changes

Clarify prior art
RFC1546 anycast
Anycast addr != unicast addr
Not widely practiced
pseudo-anycast (BGP anycast)
Use unicast address at multiple distant locations
Only for short-lived connections/sessions
Practiced for nameservers and HTTP servers
SCTP section contributed by John Loughney
Reference updates
Address other comments from IESG

I don't feel the need for another WG last call - chairs?