during execute"


mysql-test/r/ps.result:
  Test results updated (Bug#6873)
mysql-test/t/ps.test:
  A test case for Bug#6873 "PS, having with subquery, crash during execute".
sql/item_subselect.cc:
  If we transform having subtree, modify SELECT_LEX::having pointer 
  to point to the new having tree root.