- fix for bug#16423 (Events: SHOW CREATE EVENT doesn't work)
- this Changeset commits makes CREATE/UPDATE/DELETE EVENT real DDL statements
  by committing the currently open transaction before they are executed.
- this Changeset also fixes a trailing space problem since the very early days
  of the internal cron
- adds sophisticated checking of whether mysql.event was tampered accidentally
  or with purpose by an user.
- adds a lot of inline function documentation - documents everything left
  uncodumented
- INTERVAL_XXXX to XXX in I_S.EVENTS.INTERVAL_FIELD

WL#1034 (Internal CRON)