CRM-13355 - add support to retrieve non-public events

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* CRM-13355: CiviDiscount Codes Should Be Available on Non-Public Events
  http://issues.civicrm.org/jira/browse/CRM-13355
Merge pull request #1716 from dlobo/CRM-13355

CRM-13355 - add support to allow retrieval of non-public events also