Revisions: compare revisions by date in wp_ajax_revisions_data(), deprecate the $parent arg in wp_list_post_revisions() as now revisions always include a copy of the current post, props adamsilverstein, see #23901

git-svn-id: https://core.svn.wordpress.org/trunk@23975 1a063a9b-81f0-0310-95a4-ce76da25c4cd