Logged out warnings: clear previous errors when interim_login is set, see #23295

git-svn-id: http://core.svn.wordpress.org/trunk@23691 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Logged out warnings, heartbeat: remove nopriv_autosave as it doubles the functionality of the logged out warnings, move wp_ajax_nopriv_heartbeat() under No-privilege Ajax handlers in ajax-actions.php, see #23295, see #23216

git-svn-id: http://core.svn.wordpress.org/trunk@23692 1a063a9b-81f0-0310-95a4-ce76da25c4cd