Merge changes made in Gnus trunk.

Merge changes made in Gnus trunk.

nnimap.el (nnimap-open-connection): If we have gnutls loaded, then try to use that for the tls stream.
nnimap.el (nnimap-retrieve-group-data-early): Rework the marks code to heed UIDVALIDITY and find out which groups are read-only and not.
nnimap.el (nnimap-get-flags): Use the same marks parsing code as the rest of nnimap.
nnimap.el (nnmail-expiry-target-group): Say that every expiry target group is the "last".
nnir.el (nnir-engines): Fix too many arguments.
nnimap.el: Start implementing QRESYNC support.
gnus.el (gnus-group-set-parameter): Fix typo.
shr.el: Rework the way things are indented by <li> slightly.
spam.el (gnus-summary-mode-map): Bind to "$".