check for datatype in select function

as mentioned here: http://www.concrete5.org/index.php?cID=403092&editmode=

the following code would create two selected options:

```php
$fh = Loader::helper('form');

echo $fh->select(
    'test', 
    array(
        '5' => '5', 
        '5-4' => '5-4'
        ), 
    5);
```