* Renamed handler::estimate_number_of_rows to handler::estimate_rows_upper_bound function, which can also return "unknown"
 * made filesort to use full sort buffer if number of rows to sort is not known.


sql/examples/ha_tina.h:
  Renamed estimate_number_of_rows -> estimate_rows_upper_bound
sql/filesort.cc:
   * Fix for BUG#5117: made filesort() to use full sort buffer if number of rows to sort is not known.
   * Comments and assertion added
sql/ha_berkeley.cc:
  Renamed estimate_number_of_rows -> estimate_rows_upper_bound
sql/ha_berkeley.h:
  Renamed estimate_number_of_rows -> estimate_rows_upper_bound
sql/ha_innodb.cc:
  Renamed estimate_number_of_rows -> estimate_rows_upper_bound
sql/ha_innodb.h:
  Renamed estimate_number_of_rows -> estimate_rows_upper_bound
sql/handler.h:
  Renamed estimate_number_of_rows -> estimate_rows_upper_bound