Merge changes made in Gnus trunk.

Merge changes made in Gnus trunk.

nnimap.el (nnimap-update-info): When UIDNEXT is present, use that for the active.
Split -request-update-info into -request-marks and -update-info.
nnimap.el (nnimap-transform-headers): Don't bug out on invalid BODYSTRUCTUREs.
nnimap.el (nnimap-transform-headers): Unfold quoted {42} headers.
nnir.el (nnir-run-imap): Fix up nnir to work with the new nnimap.
nnimap.el (nnimap-stream): Add starttls support.
gnus-int.el (gnus-request-update-info): Protect against backends not having the function.
gnus-html.el (gnus-html-rescale-image): Revert change that uses window-inside-pixel-edges.
gnus-start.el (gnus-fixup-nnimap-unread-after-getting-new-news): Remove.
nnimap.el (nnimap-retrieve-headers): Return 'headers.
gnus-sum.el (gnus-summary-local-variables): Prepare for list/range makeover.
gnus-start.el: Add new variable gnus-use-backend-marks, and start reading marks again.