messed up

"ROW(...) IN (SELECT ... FROM DUAL)" always returned TRUE.

Item_in_subselect::row_value_transformer rewrites "ROW(...)
IN SELECT" conditions into the "EXISTS (SELECT ... HAVING ...)"
form.
For a subquery from the DUAL pseudotable resulting HAVING
condition is an expression on constant values, so further
transformation with optimize_cond() eliminates this HAVING
condition and resets JOIN::having to NULL.
Then JOIN::exec treated that NULL as an always-true-HAVING
and that caused a bug.

To distinguish an optimized out "HAVING TRUE" clause from
"HAVING FALSE" we already have the JOIN::having_value flag.
However, JOIN::exec() ignored JOIN::having_value as described
above as if it always set to COND_TRUE.

The JOIN::exec method has been modified to take into account
the value of the JOIN::having_value field.


mysql-test/r/subselect3.result:
  Added test case for bug #39069.
mysql-test/t/subselect3.test:
  Added test case for bug #39069.
sql/sql_select.cc:
  Bug #39069: <row constructor> IN <table-subquery> seriously
              messed up
  
  The JOIN::exec method has been modified to take into account
  the value of the JOIN::having_value field.