uniform disclaimer for moving specs to Standard Track

All,

>From the minutes of the Vancouver meeting:

   - all submissions transforming an Experimental into a Standard Tack
     RFC should contain the following:

     * a section "Changes since RFCXXXX"
     * A common note explaining the rationale for moving to Standard
       Track (this note will be the same in all document a will be
       drafted soon by the WG).

I'd like to propose the following text that Mark Watson and I have
come up with, please comment. The text should probably be included in
the introduction.

###########################

This specification contains part of the definitions necessary to
fully specify a Reliable Multicast Transport protocol in accordance
with RFC2357.

RFCxxxx contained a previous version of this specification, which was
published in the "Experimental" category. It was the stated intent of 
the RMT working group to re-submit this specification as an IETF
Proposed Standard in due course.

This Proposed Standard specification is thus based on RFCxxxx updated 
according to accumulated experience and growing protocol maturity
since the publication of RFCxxxx. Said experience applies both to this  
specification itself and to congestion control strategies related to
the use of this specification.

The differences between RFCxxxx and this document listed in Section X.

###########################

	Thank you,
	Lorenzo