[PATCH] lib: Improve documentation of _notmuch_message_create_for_message_id

[David Bremner]

Austin Clements <amdragon at MIT.EDU> writes:

> Clarify the state of the returned message when
> _notmuch_message_create_for_message_id returns
> NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND.

pushed,

d