Change login element into a render array so it can be editable

Currently the login button in the twitter_login module is added to the form as an item list directly inserted using #markup. This makes it uneditable anywhere down the line. The code where this happens is line 106 of twitter_login.module:

    $form['twitter_signin'] = array(
      '#markup' => theme('item_list', array('items' => $items)),
    );

I am attaching a patch to turn this into a render array:

    $form['twitter_signin'] = array(
      '#theme' => 'item_list',
      '#items' => $items,
      '#attributes' => array('class' => array('twitter_signin')),
    );