Made changes suggested by Bernie's extensive review.

Changes included these significant differences:

1. Section 2: Added "DDNS" and "Lease" to the Glossary.

2. Section 2: Included temporary (IA_TA) addresses in the resources
that are handled by failover.

3. Section 5.1: Made attempting to connect to failover partner a
MUST instead of a SHOULD, for both primary and secondary servers.

4. Section 6.1: Removed ordering requirement for POOLRESP message
to be sent prior to BNDUPD triggered by POOLREQ.  Also removed
implicit requirement (largely in figures) that POOLRESP contain
number of resources allocated to partner.

5. Section 6.3: Removed MUST requirement for proportional algorithm
support, and deferred algorithm assignment to resource allocation
domain to subsequent documents.

6. Section 8.2: Removed entire section on Time Expression.  This
will be addressed in any subsequent protocol document(s) produced.

7. Old Section 8.7 (new 8.6): Removed requirement for every server
to be able to support multiple binding update transactions in a
single message.  Instead such use is now negotiated during connection
establishment with the CONNECT and CONNECTACK message exchange.

8. Old Section 8.7 (new 8.6): Removed requirement to send the valid
life time requested by DHCPv6 client in every BNDUPD.

9. Old Section 8.7 (new 8.6): Removed requirement to reject BNDUPD
messages that contain (or do not contain) specific values.  Kept
MUST directives for what must go into the BNDUPD, but allow receiving
code to do the best it can and not be required to reject any
particular packet.

10. Old Section 8.7 (new 8.6): Removed explicit requirement for the
following data items:
 o Remote-ID, defined in [RFC4649];
 o Relay-ID, defined in [RFC5460], section 5.4.1;
 o Link-layer address [RFC6939];
and replaced it with a reference to the Relay Data option defined
in RFC 5007 (the DHCPv6 Leasequery draft).  Along with this, moved
RFC 5007 from the Informative to the Normative Bibliography section.

11. Section 9.7.1: Restricted ability of server to process messages
in RECOVER-DONE state to RENEW message with no new resource allocations
allowed even for RENEW message.

12. Section 9.11: Clarified reasoning for RESOLUTION-INTERRUPTED
state, to avoid confusion.