This patch introduces specialized Event data objects
Event_basic as parent.
Event_queue_element used for queue storage
Event_timed used for SHOW EVENTS/ I_S.EVENTS / SHOW CREATE EVENT
Event_job_data using during execution.
Methods were moved out of Event_timed to other classes.

This patch also introduces Events::LOCK_event_metadata.
This patch gives new implementation of Events::dump_internal_status().
Now both the Event_scheduler and Event_queue return information during
their ::dump_internal_status().

Shortened a bit the runtime for executing events test cases.


mysql-test/r/events.result:
  update results
mysql-test/r/events_bugs.result:
  update results
mysql-test/r/events_logs_tests.result:
  update results
mysql-test/r/events_scheduling.result:
  update results
mysql-test/t/events.test:
  update test
  make --sleep more appropriate . saving some time could mean failure on loaded boxes though :(
  add tests for previously uncovered branches.
mysql-test/t/events_bugs.test:
  update test
  make --sleep more appropriate . saving some time could mean failure on loaded boxes though :(
  add tests for previously uncovered branches.
mysql-test/t/events_logs_tests.test:
  make the test shorter by time
mysql-test/t/events_scheduling.test:
  when selecting always use ORDER BY
mysql-test/t/events_stress.test:
  sleep 2.5secs for shorter stress test
sql/event_data_objects.cc:
  Event_timed is no more used during execution.
  Event_timed is no more used during in the memory queue.
  Event_timed is only used for SHOW CREATE EVENT/ I_S.EVENTS/ SHOW EVENTS
  Event_basic is the parent of almost all Event data objects.
  Event_basic -> Event_queue_element (used for the memory queue) -> Event_timed
  Event_basic -> Event_job_data (the object used for execution)
  Sql_alloc -> Event_parse_data (used during parsing)
sql/event_data_objects.h:
  Event_timed is no more used during execution.
  Event_timed is no more used during in the memory queue.
  Event_timed is only used for SHOW CREATE EVENT/ I_S.EVENTS/ SHOW EVENTS
  Event_basic is the parent of almost all Event data objects.
  Event_basic -> Event_queue_element (used for the memory queue) -> Event_timed
  Event_basic -> Event_job_data (the object used for execution)
  Sql_alloc -> Event_parse_data (used during parsing)
sql/event_db_repository.cc:
  Cosmetics.
  load_named_event now uses Event_basic, for polymorphism
  find_event uses Event_basic, to be polymorphic.
  use Field **fields= table->field and then index fields[...]
  Add documentation.
  Fix documentation.
sql/event_db_repository.h:
  Event_db_repository depends only on Event_basic's interface
sql/event_queue.cc:
  Cosmetics.
  Don't use Event_timed for the queue and giving back object for execution.
  Event_queue_element is for the queue, Event_job_data is for execution.
  Add Event_queue::dump_internal_status() for SHOW SCHEDULER STATUS command
sql/event_queue.h:
  Cosmetics.
  Don't use Event_timed for the queue and giving back object for execution.
  Event_queue_element is for the queue, Event_job_data is for execution.
  Add Event_queue::dump_internal_status() for SHOW SCHEDULER STATUS command
sql/event_scheduler_ng.cc:
  Add back Event_scheduler::cond_wait()
  Add back Event_scheduler::dump_internal_status()
  Using Event_job_data for execution. Make the scheduler thread unkillable (thd->command= COM_DAEMON).
  Add a lot of documentation.
sql/event_scheduler_ng.h:
  Add back Event_scheduler::cond_wait()
  Add back Event_scheduler::dump_internal_status()
  Using Event_job_data for execution.
sql/events.cc:
  Documentation
  Add LOCK_event_metadata
sql/events.h:
  Change the signature of Events::drop_event() not to use sp_name but LEX_STRING
sql/share/errmsg.txt:
  Fix error message
sql/sql_parse.cc:
  Events::drop_event() has new signature