sql/sql_acl.cc:
  I revert my last change, as this requires further elaboration.
  For the moment we should document it in the manual.
  
  If MySQL 4.0.2 or higher is used with pre-4.0.2 user privilege table, 
  then user with no global privs at all will have privileges to:
  
  * LOCK TABLES
  * CREATE TEMPORARY TABLES
  * run commsnd SHOW DATABASES