Optimizer erroneously translated LEFT JOIN into INNER JOIN.
It leads to cutting rows with NULL right side. It happens
because Item_row uses not_null_tables() method form the
base(Item) class and does not calculate 'null tables'
properly. The fix is adding calculation of 'not null tables'
to Item_row.


mysql-test/r/join_outer.result:
  test result
mysql-test/t/join_outer.test:
  test case
sql/item_row.cc:
  adding calculation of 'not null tables' to Item_row.
sql/item_row.h:
  adding calculation of 'not null tables' to Item_row.