The 250 simultaneous events all accessing the same table caused the
events_stress test to fail due to debug warnings about too many table
waiters. Fixed by using three different tables.


mysql-test/r/events_stress.result:
  Use three different MyISAM tables to avoid debug warnings about too many
  locks.
mysql-test/t/events_stress.test:
  Use three different MyISAM tables to avoid debug warnings about too many
  locks.