Fix for Message ID and Sequence Number sections

I propose the attached changes for sections 3.1.1 and 3.1.2 (

This change involves:
- nesting of the existing 3.1.2 inside 3.1.1.
- the proper use of MUST, and MAY for element and attribute inclusion, and
- moving the staement on presence of group termination parameters to a 
more proper location.

Tom Rutt

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Tom Rutt		email: ; 
Tel: +1 732 801 5744          Fax: +1 732 774 5133