Added a test case for bug #8617.
sql_select.cc:
  Fixed bug #8617.
  Queries with ROLLUP and LIMIT n returned more than n rows
  if SQL_CALC_FOUND_ROWS was used.


sql/sql_select.cc:
  Fixed bug #8617.
  Queries with ROLLUP and LIMIT n returned more than n rows
  if SQL_CALC_FOUND_ROWS was used.
mysql-test/t/olap.test:
  Added a test case for bug #8617.