Improve security of sessions:

- use only cookies to store session id on client side
- use default php session system with database handler to store sessions on server side

git-svn-id: http://piwigo.org/svn/trunk@1004 68402e56-0260-453c-a942-63ccdbb3a9ee

include/category_default.inc.php

@@ -89,7 +89,7 @@ while ($row = mysql_fetch_array($result))
       'IMAGE_TITLE'        => $thumbnail_title,
       'IMAGE_TS'           => get_icon($row['date_available']),
       
-      'U_IMG_LINK'         => add_session_id($url_link)
+      'U_IMG_LINK'         => $url_link
       )
     );