outer resolved fields now do not marked as dependent if they is not really belong to outer SELECT
one-letter variables name fixed


mysql-test/r/subselect.result:
  test of bug 679
mysql-test/t/subselect.test:
  test of bug 679
sql/item.cc:
  outer resolved fields now do not marked as dependent if they is not really belong to outer SELECT
  one-letter variables name fixed