fixed bug in truncating nonexisting table, found by Carsten

mysql-test/r/truncate.result:
  test suit for truncate bug
mysql-test/t/truncate.test:
  test suit for truncate bug

mysql-test/r/truncate.result

@@ -20,3 +20,5 @@ truncate table t1;
 select * from t1;
 n
 drop table t1;
+truncate non_existing_table;
+Table 'test.non_existing_table' doesn't exist

mysql-test/t/truncate.test

@@ -18,3 +18,5 @@ insert into t1 values (1),(2),(3);
 truncate table t1;
 select * from t1;
 drop table t1;
+--error 1146
+truncate non_existing_table;

sql/sql_delete.cc

@@ -546,7 +546,8 @@ int mysql_truncate(THD *thd, TABLE_LIST *table_list, bool dont_send_ok)
     db_type table_type;
     if ((table_type=get_table_type(path)) == DB_TYPE_UNKNOWN)
     {
-      my_error(ER_NO_SUCH_TABLE, MYF(0), table_list->real_name);
+      my_error(ER_NO_SUCH_TABLE, MYF(0), table_list->db,
+	       table_list->real_name);
       DBUG_RETURN(-1);
     }
     if (!ha_supports_generate(table_type))