Acl callback assertion

[kanellov]

Like the Rbac callback assertion proposed in #7327, I've implemented an ACL Callback assertion class. Here is an example of use:

<?php
use Zend\Permissions\Acl\Acl;
use Zend\Permissions\Acl\Assertion\Callback;

$validIps = array(
    10.10.10.10,
);
$acl = new Acl();
$assertion = new Callback(function ($acl, $role, $resource, $privilege) use ($validIps) {
    return in_array($_SERVER['REMOTE_ADDR'], $validIps);
});
$acl->allow(null, null, null, $assertion);  

[weierophinney]

Merged to develop for release with 2.4.