to 5.0 tree (since it was lost during last merge).


mysql-test/r/func_sapdb.result:
  Updated test result after fixing bug #7586 "TIMEDIFF for sec+microsec not
  working properly" in 5.0 tree.
sql/item_timefunc.cc:
  calc_time_diff():
    Use simplier and less error-prone implementation. Now we are counting
    difference between time values in microseconds and then convert it to
    seconds + microseconds value (instead of using seconds and taking
    difference in "second_part"s into account).