CRM-12601 - Restore getClasses() and mitigate damage from missing function

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* CRM-12601: Test suite crashes - CRM_Core_DAO_AllCoreTables::getClasses
  http://issues.civicrm.org/jira/browse/CRM-12601
Merge pull request #731 from totten/allcoretables-fatal

CRM-12601 - Restore getClasses() and mitigate damage from missing functi...