accordint to wikipedia http://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references#Predefined_entities_in_XML all the entities we use in escapeHTML exist in XML (and they are the only one). Would make sense to add a comment in line 9 of `utils.js` saying that (eg) "we use this in XML context too (see smil.js) so if we add more entities we need to separate escapeHTML and escapeXML".