Escape story fields and clean story HTML with HTML Purifier.

Add HTML Purifier 4.19.1. Stories are purified when they are saved and
when they are shown.

lib/htmlpurifier-4.19.1/library/HTMLPurifier/ConfigSchema/schema/HTML.AllowedComments.txt

@@ -0,0 +1,10 @@
+HTML.AllowedComments
+TYPE: lookup
+VERSION: 4.4.0
+DEFAULT: array()
+--DESCRIPTION--
+A whitelist which indicates what explicit comment bodies should be
+allowed, modulo leading and trailing whitespace.  See also %HTML.AllowedCommentsRegexp
+(these directives are union'ed together, so a comment is considered
+valid if any directive deems it valid.)
+--# vim: et sw=4 sts=4