Simpler impl.

sql/sql_parse.cc:
  Just do a simple sprintf to format error message.

sql/sql_parse.cc

@@ -5499,15 +5499,13 @@ bool add_field_to_list(THD *thd, char *field_name, enum_field_types type,
        In other words, for declarations such as TIMESTAMP(2), TIMESTAMP(4),
        and so on, the display width is ignored.
     */
-    char buff[32];
-    String str(buff,(uint32) sizeof(buff), system_charset_info);
-    str.append("TIMESTAMP(");
-    str.append(length);
-    str.append(")");
+    char buf[32];
+    my_snprintf(buf, sizeof(buf),
+                "TIMESTAMP(%s)", length, system_charset_info);
     push_warning_printf(thd,MYSQL_ERROR::WARN_LEVEL_WARN,
                         ER_WARN_DEPRECATED_SYNTAX,
                         ER(ER_WARN_DEPRECATED_SYNTAX),
-                        str.c_ptr(), "TIMESTAMP");
+                        buf, "TIMESTAMP");
   }
 
   if (!(new_field= new_create_field(thd, field_name, type, length, decimals,