tmp_table_size is not about user-created temporary tables, only

internal ones (like those of GROUP BY): fixing the --help text.

sql/mysqld.cc

@@ -6181,7 +6181,8 @@ The minimum value for this variable is 4096.",
     (gptr*) &opt_date_time_formats[MYSQL_TIMESTAMP_TIME],
     0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"tmp_table_size", OPT_TMP_TABLE_SIZE,
-   "If an in-memory temporary table exceeds this size, MySQL will automatically convert it to an on-disk MyISAM table.",
+   "If an internal in-memory temporary table exceeds this size, MySQL will"
+   " automatically convert it to an on-disk MyISAM table.",
    (gptr*) &global_system_variables.tmp_table_size,
    (gptr*) &max_system_variables.tmp_table_size, 0, GET_ULL,
    REQUIRED_ARG, 32*1024*1024L, 1024, MAX_MEM_TABLE_SIZE, 0, 1, 0},