mysql-test/r/subselect.result:
  test for BUG#1484
mysql-test/t/subselect.test:
  layout fix
  test for BUG#1484
sql/set_var.cc:
  value evaluating can fail (because of subqueries for example) => we should check result of operartion and prevent assigning incorrect value
sql/sql_do.cc:
  DO should ignore all errors