Give warnings for unused objects

Changed error message to be compatible with old error file
Added new error message for new DUP_ENTRY syntax

mysql-test/t/heap_btree.test

@@ -143,7 +143,7 @@ SELECT * FROM t1 WHERE b=NULL;
 explain SELECT * FROM t1 WHERE b IS NULL;
 SELECT * FROM t1 WHERE b<=>NULL;
 
---error 1062
+--error ER_DUP_ENTRY_WITH_KEY_NAME
 INSERT INTO t1 VALUES (1,3);
 DROP TABLE t1;