Added a test case for bug #11543.
sql_select.cc:
  Fixed bug #11543.
  A ROLLUP query could return a wrong result set when
  its GROUP BY clause contained references to the same
  column.


sql/sql_select.cc:
  Fixed bug #11543.
  A ROLLUP query could return a wrong result set when
  its GROUP BY clause contained references to the same
  column.
mysql-test/t/olap.test:
  Added a test case for bug #11543.
mysql-test/r/olap.result:
  Added a test case for bug #11543.