<?php
/**
 * hook_form_alter
 */
function menu_html_form_alter(&$form, $form_state, $form_id) {
  if ($form_id == 'menu_edit_item' || strpos($form_id, '_node_form') > 0) {
    @$item = ($form_id == 'menu_edit_item' ? $form['options']['#value']['html'] : $form['menu']['link']['options']['#value']['html']);
    $form['menu']['html'] = array(
      '#type' => 'checkbox',
      '#title' => t('Allow html'),
      '#default_value' => isset($item) ? $item : 0,
      '#description' => t('If you want to add html tags to the title of a menu, enable this. This should only be accessible to trusted users.'),
      );
  }
}

/**
 * hook_menu_link_alter
 *
 */
function menu_html_menu_link_alter(&$item) {
  if (isset($item['html']) && $item['html']) {
    $item['options']['html'] = $item['html'];
  } else {
    if(isset($item['options']['html'])) {
        unset($item['options']['html']);
    }
  }
}