Don't send affected rows after CREATE/ALTER/DROP EVENT as this is
inconsistent with the rest of the server in terms of CREATE/ALTER/DROP
DDLs


sql/event_data_objects.cc:
  Events::drop_event() does not expect anymore a parameter named affected_rows
sql/event_db_repository.cc:
  Remove rows_affected as the behavior exposed by Events is not
  coherent with the behavior of many other DDL, like CREATE PROCEDURE, etc.
sql/event_db_repository.h:
  Remove rows_affected as the behavior exposed by Events is not
  coherent with the behavior of many other DDL, like CREATE PROCEDURE, etc.
sql/events.cc:
  Remove rows_affected as the behavior exposed by Events is not
  coherent with the behavior of many other DDL, like CREATE PROCEDURE, etc.
sql/events.h:
  Remove rows_affected as the behavior exposed by Events is not
  coherent with the behavior of many other DDL, like CREATE PROCEDURE, etc.
sql/sql_parse.cc:
  Don't send affected rows, because this behavior is not consistent
  with the rest of the server for CREATE/ALTER/DROP DDLs