Shepherd writeup

ISE write-up for: draft-melnikov-mmhs-authorizing-users-13

"This document describes a procedure for when an Military Message
Handling System (MMHS) message is composed by one user and is only
released to the mail transfer system when one or more authorizing
users authorize release of the message by adding the MMHS-
Authorizing-Users header field. The resulting message can be
optionally signed by the sender and/or reviewer, allowing recipients
to verify both the original signature (if any) and review signatures."

It was reviewed for me by Russ Housley and Sean Turner, its author
has made the changes discussed between them.

This draft has IANA Considerations, it asks for a new 'Provisional
Message Header Field Name, IANA have reviewed that request.