CRM-13998 - upgrade checks for missing report_instance columns.

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* CRM-13998: Upgrade is missing alter statements for civicrm_report_instance
  http://issues.civicrm.org/jira/browse/CRM-13998
Merge pull request #2369 from davecivicrm/CRM-13998

CRM-13998 - upgrade checks for missing report_instance columns.