Fixes #1391: CDetailView: callables (including anonymous functions for PHP 5.3+) could be used as value generators of the attributes.

Fixes #1391.

Testing code:
```php
<?php $this->widget('zii.widgets.CDetailView',array(
	'data'=>TaskGroup::model()->find(array('offset'=>1)),
	'attributes'=>array(
		'id',
		'title',
		'create_time',
		array(
			'name'=>'update_time',
			'value'=>function($data) {
				return $data->id.', '.$data->title;
			},
		),
	),
)); ?>

<br/><br/>

<?php
class TestingClass
{
	public static function testingCallback($data)
	{
		return $data->id.', '.$data->title;
	}
}
?>

<?php $this->widget('zii.widgets.CDetailView',array(
	'data'=>TaskGroup::model()->find(array('offset'=>1)),
	'attributes'=>array(
		'id',
		'title',
		'create_time',
		array(
			'name'=>'update_time',
			'value'=>array('TestingClass','testingCallback'),
		),
	),
)); ?>
```