constant outer tables did not return null complemented
rows when conditions were evaluated to FALSE.
Wrong results were returned because the conditions over constant
outer tables, when being pushed down, were erroneously enclosed 
into the guard function used for WHERE conditions.


mysql-test/r/join_outer.result:
  Added a test case for bug #28571.
mysql-test/t/join_outer.test:
  Added a test case for bug #28571.
sql/sql_select.cc:
  Fixed bug #28571. Outer join queries with ON conditions over
  constant outer tables did not return null complemented
  rows when conditions were evaluated to FALSE.
  Wrong results were returned because the conditions over constant
  outer tables, when being pushed down, were erroneously enclosed 
  into the guard function used for WHERE conditions.
  The problem is fixed in the function make_join_select. Now the
  conditions over constant tables from ON expressions are pushed
  down after the conditions from WHERE has been pushed down.