SHOW AUTHORS caused 'Packets out of order' in stored functions:
add the corresponding SQLCOM to sp_get_flags_for_command so that
it'd return sp-related flags for it. 
Fix Bug#17403 "Events: packets out of order with show create event"
in the same chaneset.


mysql-test/r/events.result:
  Update the results (Bug#17403)
mysql-test/r/sp-error.result:
  Test results fixed (Bug#16164)
mysql-test/t/events.test:
  Add a test case for Bug#17403 "Events: packets out of order with
  show create event"
mysql-test/t/sp-error.test:
  Add a test case for Bug#16164 "Easter egg"
sql/sp_head.cc:
  Add SHOW AUTHORS to the list of commands that return a result
  set: such commands are not allowed in stored functions and
  triggers. Add SHOW CREATE EVENT for the same reason.