CRM-12867

Problem was that in alterDisplay we try to suppress some rows, concluding duplicate or repetition. Final count (displayed in stats) is different from those present in temp table (displayed as pager) and therefore a mismatch.
The included fix does a group by on temp table so $rows in php and number of records in temp table match.

Another fix was made to consider group by of 'altered_contact_id' instead of 'entity_id' which gave better / less-repetitive results.
For example - just an email update of a contact - updates contact, email and custom (assuming 1 custom table) tables - a total of 3 tables. And the log report would show the update logs 3 times instead of 1.

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* CRM-12867:  Changelog enhanced summary report: pagination erroneous count
  http://issues.civicrm.org/jira/browse/CRM-12867