New field "guid" added to table user.

This can be userd to store "global unique identifier" from external databases
like Windows SID or eDirectorys guid . This will keep upcoming user syncronization
feature reliable in case of renamed users.
Mysql files are untested.
php -l mysql.php does not show any syntax errors, so files
should work.

lib/db/mysql.sql

@@ -308,6 +308,7 @@ CREATE TABLE `prefix_scale` (
 CREATE TABLE `prefix_user` (
   `id` int(10) unsigned NOT NULL auto_increment,
   `auth` varchar(20) NOT NULL default 'manual',
+  `guid` varchar(128) default NULL,
   `confirmed` tinyint(1) NOT NULL default '0',
   `deleted` tinyint(1) NOT NULL default '0',
   `username` varchar(100) NOT NULL default '',
@@ -346,6 +347,8 @@ CREATE TABLE `prefix_user` (
   UNIQUE KEY `id` (`id`),
   UNIQUE KEY `username` (`username`)
 ) TYPE=MyISAM COMMENT='One record for each person';
+
+ALTER TABLE `prefix_user` ADD INDEX `authguid` (`auth`, `guid`);
 # --------------------------------------------------------
 
 #