Merge changes made in Gnus trunk.

shr.el (shr-render-td): Use a cache for the table rendering function to avoid getting an exponential rendering behaviour in nested tables.
shr.el (shr-insert): Rework the line-breaking algorithm.
shr.el (shr-insert): Don't leave trailing spaces.
shr.el (shr-insert-table): Also insert empty TDs.
shr.el (shr-tag-blockquote): Ensure paragraphs after </ul>.
gnus-start.el (gnus-get-unread-articles): Require gnus-agent before bidning gnus-agent variables.
mm-decode.el (mm-save-part): If given a non-directory result, expand the file name before using to avoid setting mm-default-directory to nil.
gnus.el (gnus-carpal): The carpal mode has been removed, but define the variable for backwards compatability.
nnimap.el (nnimap-update-info): Remove double setting of high.
nnimap.el (nnimap-update-info): Don't ignore groups that have no UIDNEXT.
shr.el (require): Require cl when compiling.
shr.el (shr-tag-hr): New function.

lisp/gnus/nnimap.el

@@ -1016,8 +1016,10 @@ textual parts.")
 
 (defun nnimap-update-info (info marks)
   (when (and marks
-	     ;; Ignore groups with no UIDNEXT values.
-	     (nth 4 marks))
+	     ;; Ignore groups with no UIDNEXT/marks.  This happens for
+	     ;; completely empty groups.
+	     (or (car marks)
+		 (nth 4 marks)))
     (destructuring-bind (existing flags high low uidnext start-article
 				  permanent-flags) marks
       (let ((group (gnus-info-group info))
@@ -1044,9 +1046,6 @@ textual parts.")
 	   group
 	   (cons (car (gnus-active group))
 		 (or high (1- uidnext)))))
-	(when (and (not high)
-		   uidnext)
-	  (setq high (1- uidnext)))
 	;; Then update the list of read articles.
 	(let* ((unread
 		(gnus-compress-sequence