* gnus-group.el (gnus-group-mark-article-read): Nreverse

	* gnus-group.el (gnus-group-mark-article-read): Nreverse
	gnus-newsgroups-unselected.

	* gnus-agent.el (gnus-summary-set-agent-mark): Use
	gnus-add-to-sorted-list.

	* gnus-sum.el (gnus-summary-update-info): gnus-newsgroup-unreads
	gnus-newsgroup-unselected are sorted. Use gnus-sorted-union.
	(gnus-build-all-threads): Use gnus-add-to-sorted-list.
	(gnus-update-read-articles): UNREAD is sorted.
	(gnus-newsgroup-unreads, gnus-newsgroup-unselected)
	(gnus-newsgroup-marked, gnus-newsgroup-cached)
	(gnus-newsgroup-expirable, gnus-newsgroup-downloadable)
	(gnus-newsgroup-dormant): Require sorted.