[ticket/11103] Add is_disabled column to notifications table

EXTENSION AUTHORS TAKE NOTE! This is to prevent errors with notifications
from extensions!

Set is_disabled to 1 for all your notifications when your extension is
disabled so they are ignored and do not cause errors.

When your extension is enabled again, set is_disabled to 0 and your
notifications will be working again.

PHPBB3-11103

phpBB/develop/create_schema_files.php

@@ -1303,6 +1303,7 @@ function get_schema_struct()
 			'item_parent_id'	=> array('UINT', 0),
 			'user_id'			=> array('UINT', 0),
 			'unread'			=> array('BOOL', 1),
+			'is_disabled'		=> array('BOOL', 0),
 			'time'				=> array('TIMESTAMP', 1),
 			'data'				=> array('TEXT_UNI', ''),
 		),
@@ -1314,6 +1315,7 @@ function get_schema_struct()
 			'user_id'			=> array('INDEX', 'user_id'),
 			'time'				=> array('INDEX', 'time'),
 			'unread'			=> array('INDEX', 'unread'),
+			'is_disabled'		=> array('INDEX', 'is_disabled'),
 		),
 	);