The code in opt_sum_query that prevented the COUNT/MIN/MAX 
optimization from being applied to outer joins  was not adjusted 
after introducing nested joins. As a result if an outer join
contained a reference to a view as an inner table the code of
opt_sum_query missed the presence of an on expressions and
erroneously applied the mentioned optimization.


mysql-test/r/view.result:
  Added a test case for bug #18237.
mysql-test/t/view.test:
  Added a test case for bug #18237.