Allow passing server parameters on form submit

[soullivaneuh]

When you do something like this:

$form = $crawler->selectButton('Submit')->form();
$crawler = $client->submit($form, [
    'foo' => 'bar',
]);

You can't pass any server value. But it can be useful, for example, to passe XHR header: https://stackoverflow.com/a/9505494/1731473

Current possible workaround:

$crawler = $client->request($form->getMethod(), $form->getUri(), $form->getPhpValues(), $form->getPhpFiles(), [
    'HTTP_X-Requested-With' => 'XMLHttpRequest',
]);