Fixed bug #14274: a query with a having clause containing only set function returned a wrong result set.


mysql-test/r/having.result:
  Added a test case for bug #14274.
mysql-test/t/having.test:
  Added a test case for bug #14274.
sql/sql_select.cc:
  Fixed bug #14274: a query with a having clause containing only set function returned a wrong result set.
  It happened because processing of the set functions in having started with a call of the split_sum_func
  method, instead of the split_sum_func2 method.