Forum RSS feed invalid

[Nicolas]

If a forum post contains an ampersand, it will end in the RSS feed unescaped, which usually would cause an invalid XML entity. Many RSS readers will then fail to load the feed at all.

If a forum post contains an HTML-like tag (like <rant> or <sarcasm>!), it will get removed, and won't show up in the feed.

The attached patch removes the use of strip_tags, and instead, escapes XML-unsafe characters.

Note that the escaping is done twice. If unescaped, the XML parser will interpret it. If escaped once, the feed reader will take it as HTML (that's RSS for ya). So we need double escaping.

[davea]

(In [18190]) - web: escape forum RSS entries instead of stripping tags

(from Nicolas; fixes #899)