Merge changes made in Gnus trunk.

Merge changes made in Gnus trunk.

mm-decode.el (mm-shr): Bind shr-blocked-images to gnus-blocked-images.
shr.el (shr-tag-table): Put all the images after the table.
shr.el (shr-tag-table): Really inhibit images inside the table.
shr.el (shr-collect-overlays): Copy over overlays from the TD elements to the main document.
nnimap.el (nnimap-request-newgroups): Return success.
gnus-group.el (gnus-group-make-group): Doc fix.
nnir.el (nnir-retrieve-headers): Don't bug out on invalid data.
gnus-sum.el (gnus-article-sort-by-most-recent-date): New function, added for symmetry.
mm-decode.el (mm-shr): Allow displaying cid: images from shr.el.
shr.el (shr-insert-table): Bind free variable.
gnus-art.el (gnus-blocked-images): Move variable here.
mm-decode.el (mm-shr): Require shr.
shr.el (shr-tag-img): Shorten ALT texts and allow them to be line-broken.
shr.el (shr-tag-img): Ignore image fetching errors.
shr.el (shr-overlays-in-region): Compute overlay positions correctly.
gnus-html.el (gnus-html-schedule-image-fetching): Protect against invalid URLs.