(after review commit)


mysql-test/r/show_check.result:
  test the extended functionality (so far not documented) of SHOW OPEN FILES
mysql-test/t/show_check.test:
  test the extended functionality (so far not documented) of SHOW OPEN FILES
sql/mysql_priv.h:
  pass the name of the database for checking
sql/sql_base.cc:
  first check against the db if present (SHOW OPEN FILES FROM xxx)
  then do wild compare but only against the table name
sql/sql_show.cc:
  pass the DB if specified