* imap.el (imap-parse-resp-text-code): The UNSEEN value in

* imap.el (imap-parse-resp-text-code): The UNSEEN value in
SELECT/EXAMINE is first unseen article, not number of unseen
articles.  Make them distinct by renaming the former to
`first-unseen' instead of `unseen'.

* nnimap.el (nnimap-retrieve-groups): Get uidvalidity and unseen
too.
(nnimap-retrieve-groups): Don't used cached data if uidvalidity
changed.
(nnimap-retrieve-groups): Store uidvalidity and unseen data too.