cakephp/cakephp — pull request #4201 by dakota (2014-08-08 14:26:40+00:00)
Title: Only add 'day' once with SqlServer DATEDIFF

If a single instance of a DATEDIFF Expression was used more than once, 'day' would be added multiple times (Once be usage). This threw an SQLServer error.

A simplistic example:
```
$age = $query->func()->dateDiff([
'Jobs.date_queued' => 'literal',
$functionBuilder->now('date'),
]);
$between30And60 = $query->newExpr()
->lte(30, $age)
->gt(60, $age);
```

This PR, in conjunction with PR #4200 allows for this use case.