initStruct(): use multiopt for 'id' 'dont_write_to_db'

This also means we can drop the 0 for not_in_db because this is the
default.

model/FetchmailHandler.php

@@ -20,7 +20,8 @@ class FetchmailHandler extends PFAHandler {
         $this->struct=array(
             # field name                allow       display in...   type    $PALANG label                     $PALANG description                 default / options / ...
             #                           editing?    form    list
-            'id'               => pacol(0,          0,      1,      'num' , ''                              , ''                                , '', array(), 0, 1),
+            'id'               => pacol(0,          0,      1,      'num' , ''                              , ''                                , '', array(),
+                array('dont_write_to_db' => 1) ),
             'domain'           => pacol(0,          0,      1,      'text', ''                              , ''                                ),
             'mailbox'          => pacol(1,          1,      1,      'enum', 'pFetchmail_field_mailbox'      , 'pFetchmail_desc_mailbox'         ), # mailbox list
             'src_server'       => pacol(1,          1,      1,      'text', 'pFetchmail_field_src_server'   , 'pFetchmail_desc_src_server'      ),