subqueries in WHERE conditions.
This bug was introduced by the patch for bug 27321.


mysql-test/r/subselect.result:
  Added a test case for bug #28337.
mysql-test/t/subselect.test:
  Added a test case for bug #28337.
sql/item.cc:
  Fixed bug #28337: wrong results for grouping queries with correlated
  subqueries in WHERE conditions.
  This bug was introduced by the patch for bug 27321.
  
  Now in the Item_field::fix_outer_field function we create an Item_outer_ref
  object for an outer reference only if it is used in the SELECT list or
  in the HAVING clause of the subquery against which the reference is resolved.