Add an entity token for the display_url

It would be incredibly useful to have an entity token available for the display_url. [node:field-link:url] strips the query string from the URL, which makes it difficult to use it as a replacement in Linked Field, Views and elsewhere.

I can't make a patch, but the following changes seem to do the trick:

Adding 'display_url' to the array at line 1088 in function link_field_item_create():

return array('title' => NULL, 'url' => NULL, 'display_url' => NULL);

Adding the $properties['display_url'] array at line 1105 in function link_field_item_property_info():

  $properties['display_url'] = array(
    'type' => 'uri',
    'label' => t('The full URL of the link.'),
    'setter callback' => 'entity_property_verbatim_set',
  );