// add tag and category support to pages
function tags_categories_support_all() {
  register_taxonomy_for_object_type('post_tag', 'page');
  register_taxonomy_for_object_type('category', 'page');
}

// ensure all tags and categories are included in queries
/*function tags_categories_support_query($wp_query) {
  if ($wp_query->get('tag')) $wp_query->set('post_type', 'any');
  if ($wp_query->get('category_name')) $wp_query->set('post_type', 'any');
}*/

// ensure all tags and categories are included in queries
function tags_categories_support_query($wp_query) {
  if ($wp_query->get('tag')) $wp_query->set('post_type', 'page');
  if ($wp_query->get('category_name')) $wp_query->set('post_type', 'page');
}

// tag and category hooks
add_action('init', 'tags_categories_support_all');
add_action('pre_get_posts', 'tags_categories_support_query');