Use link field widget in custom form

I created a patch to allow to use all the link field widget options in a custom form.
This patch is not perfect, but I think it's a good start. Note: I didn't test it with a multi valued widget instance.

Example of implementation in an admin settings form.

/**
 * Settings for my_module.
 */
function my_module_settings_form() {
  $form['my_module_custom_link'] = array(
    // Required so all the field values are put in a single variable in $form_state.
    '#tree' => TRUE, 

    '#type' => 'link_field',
    '#title' => $value,
    '#default_value' => variable_get('my_module_custom_link'),

    // New properties.
    '#title_maxlength' => 30,
    '#attributes' => array(
       'target' => LINK_TARGET_USER,
    ), 
    
    // Required properties, if omitted, php notices are thrown.
    '#delta' => 0,
    '#language' => 'und',
    '#field_parents' => array(),
    '#field_name' => 'link_field',
  );

  return system_settings_form($form);
}

New properties are:

• #title_maxlength : integer, set the title field maxlength, default to 128
• #title_label_use_field_label : bool, use field label instead of "Title" for title field label, default to false
• #title_mode : string, possible values: 'optional', 'required', default to 'optional'
• #url : string, possible values: 'optional', 'required', default to 'optional'
• #attributes : array, set widget attributes.

Available attributes are:

• target : display a checkbox to set the final link href target attribute or directly set it
• configurable_title : display a textfield to set the final link title attribute
• configurable_class : display a textfield to set a custom class on final link

In the form_submit functions, all the field values will be stored in $form_state['my_custom_link'] as an array.