some plugins might use own hooks

doc/plugin.txt

@@ -324,12 +324,14 @@ but may be out of date soon thereafter.  You never know.  ;-)
   webmail_top                    src/webmail.php                 do_hook
   webmail_bottom                 src/webmail.php                 concat_hook
   logout_above_text              src/signout.php                 concat_hook
+  O info_bottom                  plugins/info/options.php        do_hook
    
 % = This hook is used in multiple places in the given file
 # = Called with hook type (see below)
 & = Special identity hooks (see below)
 ^ = Special attachments hook (see below)
 * = Special options hooks (see below)
+O = optional hook used by plugin
 
 
 (#) Called With