Description:
------------
func_get_args() and func_get_arg() should return variables by reference.

Reproduce code:
---------------
<?php

$one = 'one';
$two = 'two';
$three = 'three';

function change_one_into_two_normal(&$var)
{
$var = 'two';
}

function change_one_into_two_using_get_args()
{
$args = func_get_args();
$args[0] = 'two';
}

change_one_into_two_normal($one);
echo $one;

$one = 'one';

change_one_into_two_using_get_args($one);
echo $one;

Expected result:
----------------
two
one

Actual result:
--------------
two
two