updated State-Info proposal

I have incorporated Bob Wyman's suggestion, reworded the User Agent
section (now 4.2, formerly 3.2) and added Abstract and Security
Considerations sections.  I will submit the current version as an
Internet Draft shortly.  (The format of the document changed slightly
to reflect presumed I-D filenames.)

	http://www.research.att.com/~dmk/session.html

Dave Kristol