Clarifications to 2.6.12

From Steve Huston's comments:

Part 2, section 6.12, 2nd para: mentions message state, but that hasn't
been defined and isn't nearby - what is it?

PROPOSED FIX: Change "its" to "the delivery's"

Part 2, section 6.12, 6th para: How can a message spontaneously attain a
terminal state?

PROPOSED FIX: add (e.g., through the expiry of TTL at the sender)

Part 2, section 6.12, 10th para, 2nd sentence: "In this case the Sender
should send..." - should "should" be "MUST" and "but not settle" be "and
MUST NOT settle"?

PROPOSED FIX: Make clearer the transition from normative definition to narrative example (somewhere near the start of 6.12)
Part 2, section 6.7 and section 7.4, delivery-count: It would be helpful
to explicitly state what is included in this count.