Description:
------------
Using unserialize_callback_func in a htaccess has no effect. The required classes do not get loaded.

Reproduce code:
---------------
** .htacces
php_value unserialize_callback_func "myCallBack"
php_flag session.auto_start On

** index.php
<?php

    function __autoload($class)
    {
        require_once './' . $class . '.php';
    }

    function myCallBack($class)
    {
        __autoload($class);
    }

    if (isset($_GET['kill'])) {
        session_destroy();
        session_start();
    }

    echo '<pre>';
    echo 'unserialize_callback_func: ' . ini_get('unserialize_callback_func') . "\n";

    echo '$_SESSION: ' . "\n";
    print_r($_SESSION);

    if (!isset($_SESSION['test'])) {
        $_SESSION['test'] = new MyClass;
        echo 'Created a ' . get_class($_SESSION['test']) . "\n";
        echo '$_SESSION: ' . "\n";
        print_r($_SESSION);
    }

    echo '<p><a href="?kill=true">Kill session</a></p>';
    echo '<p><a href="' . $_SERVER['PHP_SELF'] . '">Reload</a></p>';
    echo '</pre>';

?>

** MyClass.php
<?php

    class MyClass
    {
        public $test = 'TestValue';
    }

?>

Expected result:
----------------
During unserialization myCallBack should be called and a complete MyClass object should exist.

$_SESSION = Array
(
    [test] => MyClass Object
        (
            [test] => TestValue
        )

)

Actual result:
--------------
$_SESSION = Array
(
    [test] => __PHP_Incomplete_Class Object
        (
            [__PHP_Incomplete_Class_Name] => MyClass
            [test] => TestValue
        )

)