Backport of:

----------------------------------------------------------
revno: 2617.23.22
committer: Konstantin Osipov <kostja@sun.com>
branch nick: mysql-6.0-runtime
timestamp: Wed 2009-03-04 23:29:16 +0300
message:
  WL#4284, "Transactional DDL locking": fix a Windows compilation warning.

sql/mdl.h

@@ -148,8 +148,9 @@ struct I_P_List_adapter
   or destructor for it.
 */
 
-struct MDL_request
+class MDL_request
 {
+public:
   /** Type of metadata lock. */
   enum          enum_mdl_type type;
 

sql/table.h

@@ -30,8 +30,8 @@ class st_select_lex;
 class partition_info;
 class COND_EQUAL;
 class Security_context;
-struct MDL_request;
-struct MDL_ticket;
+class MDL_request;
+class MDL_ticket;
 
 /*************************************************************************/