* doc/lispref/text.texi (Parsing HTML/XML): Mention that
discard-comments is obsolete.
* lisp/xml.el (xml-remove-comments): New function (bug#27178).
* src/xml.c (Flibxml_parse_html_region): Clarify what
DISCARD-COMMENTS actually does, and say that the parameter is
obsolete.
(Flibxml_parse_xml_region): Ditto.