Merge weblab.(none):/home/marcsql/TREE/mysql-5.0-21904_b

into  weblab.(none):/home/marcsql/TREE/mysql-5.1-21904_b-merge


mysql-test/r/subselect.result:
  Auto merged
mysql-test/t/subselect.test:
  Auto merged
sql/item_subselect.cc:
  Auto merged
sql/item_subselect.h:
  Auto merged
sql/sql_cache.cc:
  Auto merged
sql/sql_yacc.yy:
  Auto merged

sql/item_subselect.h

@@ -180,7 +180,11 @@ class Item_singlerow_subselect :public Item_subselect
     rewriting, mandated by a SQL:2003 exception in the specification.
     The only caller of this method is handle_sql2003_note184_exception(),
     see the code there for more details.
-    Do not call this method for other purposes.
+    Note that this method breaks the object internal integrity, by
+    removing it's association with the corresponding SELECT_LEX,
+    making this object orphan from the parse tree.
+    No other method, beside the destructor, should be called on this
+    object, as it is now invalid.
     @return the SELECT_LEX structure that was given in the constructor.
   */
   st_select_lex* invalidate_and_restore_select_lex();