gnus: replace cl with cl-lib

* lisp/gnus/gnus-agent.el, lisp/gnus/gnus-art.el:
* lisp/gnus/gnus-async.el, lisp/gnus/gnus-cache.el:
* lisp/gnus/gnus-demon.el, lisp/gnus/gnus-group.el:
* lisp/gnus/gnus-icalendar.el, lisp/gnus/gnus-logic.el:
* lisp/gnus/gnus-msg.el, lisp/gnus/gnus-picon.el:
* lisp/gnus/gnus-registry.el, lisp/gnus/gnus-salt.el:
* lisp/gnus/gnus-score.el, lisp/gnus/gnus-spec.el:
* lisp/gnus/gnus-srvr.el, lisp/gnus/gnus-start.el:
* lisp/gnus/gnus-sum.el, lisp/gnus/gnus-topic.el:
* lisp/gnus/gnus-util.el, lisp/gnus/gnus-uu.el, lisp/gnus/gnus-win.el:
* lisp/gnus/mail-source.el, lisp/gnus/mm-decode.el:
* lisp/gnus/mm-encode.el, lisp/gnus/mm-url.el, lisp/gnus/mm-view.el:
* lisp/gnus/mml-smime.el, lisp/gnus/mml.el, lisp/gnus/mml2015.el:
* lisp/gnus/nnbabyl.el, lisp/gnus/nndoc.el, lisp/gnus/nneething.el:
* lisp/gnus/nnheader.el, lisp/gnus/nnimap.el, lisp/gnus/nnmail.el:
* lisp/gnus/nnmaildir.el, lisp/gnus/nnoo.el, lisp/gnus/nnrss.el:
* lisp/gnus/nnspool.el, lisp/gnus/nntp.el, lisp/gnus/nnvirtual.el:
* lisp/gnus/nnweb.el, lisp/gnus/spam.el: Replace cl with cl-lib.
* lisp/gnus/canlock.el, lisp/gnus/gnus-bcklg.el:
* lisp/gnus/gnus-cite.el, lisp/gnus/gnus-cloud.el:
* lisp/gnus/gnus-draft.el, lisp/gnus/gnus-dup.el:
* lisp/gnus/gnus-fun.el, lisp/gnus/gnus-html.el:
* lisp/gnus/gnus-int.el, lisp/gnus/gnus-kill.el, lisp/gnus/gnus-ml.el:
* lisp/gnus/gnus-mlspl.el, lisp/gnus/gnus-range.el:
* lisp/gnus/gnus-undo.el, lisp/gnus/gnus-vm.el:
* lisp/gnus/mm-partial.el, lisp/gnus/mm-uu.el, lisp/gnus/mml1991.el:
* lisp/gnus/nnagent.el, lisp/gnus/nndiary.el, lisp/gnus/nndir.el:
* lisp/gnus/nndraft.el, lisp/gnus/nnfolder.el, lisp/gnus/nngateway.el:
* lisp/gnus/nnmairix.el, lisp/gnus/nnmbox.el, lisp/gnus/nnmh.el:
* lisp/gnus/nnml.el, lisp/gnus/score-mode.el, lisp/gnus/smiley.el:
No need for cl.

lisp/gnus/gnus-async.el

@@ -24,7 +24,7 @@
 
 ;;; Code:
 
-(eval-when-compile (require 'cl))
+(eval-when-compile (require 'cl-lib))
 
 (require 'gnus)
 (require 'gnus-sum)
@@ -183,7 +183,7 @@ that was fetched."
 		    d)
 		(while (and (setq d (pop data))
 			    (if (numberp n)
-				(natnump (decf n))
+				(natnump (cl-decf n))
 			      n))
 		  (unless (or (gnus-async-prefetched-article-entry
 			       group (setq article (gnus-data-number d)))
@@ -290,7 +290,7 @@ that was fetched."
 	    ;; should check time-since-last-output, which
 	    ;; needs to be done in nntp.el.
 	    (while (eq article gnus-async-current-prefetch-article)
-	      (incf tries)
+	      (cl-incf tries)
 	      (when (nntp-accept-process-output proc)
 		(setq tries 0))
 	      (when (and (not nntp-have-messaged)