A fix for a bug with derived tables within subselect

within derived tables within ......

mysql-test/r/derived.result

@@ -65,3 +65,6 @@ a	t
 19	19
 20	20
 drop table if exists  t1;
+SELECT * FROM (SELECT (SELECT * FROM (SELECT 1 as a)));
+(SELECT * FROM (SELECT 1 as a))
+1

mysql-test/t/derived.test

@@ -34,3 +34,4 @@ while ($1)
 enable_query_log;
 SELECT * FROM (SELECT * FROM t1) ORDER BY a  ASC LIMIT 0,20;
 drop table if exists  t1;
+SELECT * FROM (SELECT (SELECT * FROM (SELECT 1 as a)));

sql/sql_derived.cc

@@ -50,7 +50,10 @@ int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit, TABLE_LIST *t)
   if (res)
     DBUG_RETURN(-1);
 
-  for (TABLE_LIST *cursor= (TABLE_LIST *)tables;
+  for (SELECT_LEX *ssl= sl; ssl; ssl= ssl->next_select_in_list())
+  {
+    TABLE_LIST *t_tables= (TABLE_LIST *)ssl->table_list.first;
+    for (TABLE_LIST *cursor= (TABLE_LIST *)t_tables;
 	 cursor;
 	 cursor=cursor->next)
     {
@@ -61,6 +64,7 @@ int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit, TABLE_LIST *t)
 	if (res) DBUG_RETURN(res);
       }
     }
+  }
   Item *item;
   List_iterator<Item> it(sl->item_list);