Code get_best_combination() computes aggr_tables incorrectly

   /*

    Additional plan nodes for postjoin tmp tables:

      1? + // For GROUP BY

      1? + // For DISTINCT

      1? + // For aggregation functions aggregated in outer query

           // when used with distinct

      1? + // For ORDER BY

      1?   // buffer result

    Up to 2 tmp tables are actually used, but it's hard to tell exact number

    at this stage.

  */

  uint aggr_tables= (group_list ? 1 : 0) +

                    (select_distinct ?

                     (tmp_table_param.using_outer_summary_function ? 2 : 1) : 0) +

                    (order ? 1 : 0) +

       (select_options & (SELECT_BIG_RESULT | OPTION_BUFFER_RESULT) ? 1 : 0) ;