[WP] Allow (optionally?) a limited set of HTML markup in node titles.

This is basically a request to include the functionality of https://www.drupal.org/project/html_title into core, to allow portions of the node title to be italicized/bolded/sub-superscripted etc.

Drupal node titles are restrictive and do not support italicized text or superscript text (e.g., Book titles, trademark symbols). The HTML Title module allows a limited set of HTML markup (em, sub, sup, b, i, strong, cite, code, bdi, wbr) to be used in node titles. It filters all other markup from titles to prevent XSS vulnerabilities or irrational nesting (e.g., links within links).