Support packing system messages into the session

Messages are extracted on post-action redirect.

main.inc.php

@@ -43,4 +43,12 @@ $_POST=Format::strip_slashes($_POST);
 $_GET=Format::strip_slashes($_GET);
 $_REQUEST=Format::strip_slashes($_REQUEST);
 }
+
+// extract system messages
+$errors = array();
+$msg=$warn=$sysnotice='';
+if ($_SESSION['::sysmsgs']) {
+    extract($_SESSION['::sysmsgs']);
+    unset($_SESSION['::sysmsgs']);
+}
 ?>

scp/staff.inc.php

@@ -110,9 +110,6 @@ $_SESSION['TZ_DST']=$thisstaff->observeDaylight();
 
 define('PAGE_LIMIT', $thisstaff->getPageLimit()?$thisstaff->getPageLimit():DEFAULT_PAGE_LIMIT);
 
-//Clear some vars. we use in all pages.
-$errors=array();
-$msg=$warn=$sysnotice='';
 $tabs=array();
 $submenu=array();
 $exempt = in_array(basename($_SERVER['SCRIPT_NAME']), array('logout.php', 'ajax.php', 'logs.php', 'upgrade.php'));