S9 LIB  (htmlify-char char)      ==>  string
        (htmlify-string string)  ==>  string

HTMLIFY-CHAR converts a char to a string that is save for
inclusion in an HTML document. HTMLIFY-STRING does the
same for a string.

(htmlify-char #\<)      ==>  "&lt;"
(htmlify-string "<&>")  ==>  "&lt;&amp;&gt;"
