The problem was that the events_bugs test could randomly fail due to
races in the test case.

The solution is to replace fixed sleeps with reliable polling of a
certain state to settle.  For that, a new auxiliary script
include/wait_condition.inc is used, that allows waiting for a given
query to return true.


mysql-test/include/wait_until_rows_count.inc:
  Script is rewritten using new include/wait_condition.inc.
mysql-test/r/events_bugs.result:
  Update result: add missing quotation mark.
mysql-test/t/events_bugs.test:
  Replace --sleep with the reliable waiting for a certain state.
mysql-test/include/wait_condition.inc:
  New BitKeeper file ``mysql-test/include/wait_condition.inc''