Added a test case for bug #8392.
sql_delete.cc:
  Fixed bug #8392.
  The bug caused a crash for a delete statement with ORDER BY
  that explicitly referred to the modified table.


sql/sql_delete.cc:
  Fixed bug #8392.
  The bug caused a crash for a delete statement with ORDER BY
  that explicitly referred to the modified table.
mysql-test/t/delete.test:
  Added a test case for bug #8392.
mysql-test/r/delete.result:
  Added a test case for bug #8392.