Updates to Renew/Rebind processing:
- server may return NoAddrsAvail status code
- provided updates to the text about receipt of Reply messages
- provided text to replace whole RFC3315 sections: 18.1.3, 18.1.4, 18.1.8, 18.2.3, 18.2.4

This text still has some outstanding issues raised by Bernie. These issues
are included as comments in XML file.