sql/ha_myisam.h:
  cleanup
mysql-test/r/bdb.result:
  bug#4089
mysql-test/t/bdb.test:
  bug#4089
sql/opt_range.cc:
  be sloppy
sql/sql_select.cc:
  JOIN::join_free - pass it down the tree (of selects)
  call mysql_unlock_tables only in top-level select