replication updates. This changeset seems to be working fine on test systems.

If no problems are discovered in the next week, this will make the replication
code ready for 4.0.2 release.

sql/sql_class.h

@@ -251,6 +251,11 @@ public:
 
 class delayed_insert;
 
+#define THD_SENTRY_MAGIC 0xfeedd1ff
+#define THD_SENTRY_GONE  0xdeadbeef
+
+#define THD_CHECK_SENTRY(thd) DBUG_ASSERT(thd->dbug_sentry == THD_SENTRY_MAGIC)
+
 /* For each client connection we create a separate thread with THD serving as
    a thread/connection descriptor */
 
@@ -312,6 +317,9 @@ public:
   // TODO: document the variables below
   MYSQL_LOCK *lock,*locked_tables;
   ULL	  *ull;
+#ifndef DBUG_OFF
+  uint dbug_sentry; // watch out for memory corruption
+#endif  
   struct st_my_thread_var *mysys_var;
   enum enum_server_command command;
   uint32 server_id;