Modify schema to get install/upgrade work with db-mssql.

Although the problem appears in step 209, the real cause is the
combination of steps 200 and 201. The Index ('user_id','name')
created in step 201 (with a nullable 'user_id' as of step 200)
forbids the alteration of 'user_id' to NOTNULL in step 209, at
least with mssql. So fix this in step 200 and set 'user_id'
NOTNULL right from start.

While this is a 'post release' change, it is justifiable as it
happens in the same install/upgrade sequence and the final
db (schema) is identical.

Fixes #22063

admin/schema.php

@@ -846,7 +846,7 @@
 #
 $g_upgrade[200] = array('CreateTableSQL', array( db_get_table( 'api_token' ), "
 	id						I		UNSIGNED NOTNULL PRIMARY AUTOINCREMENT,
-	user_id					I		DEFAULT '0',
+	user_id					I		NOTNULL DEFAULT '0',
 	name					C(128)	NOTNULL,
 	hash					C(128)	NOTNULL,
 	date_created			I		UNSIGNED NOTNULL DEFAULT '0',