[XML-SIG] XML 0.5.1 bug: 'amp' character reference not handled correctly by "HtmlBuilder/HtmlWriter"

[Dieter Maurer]

"HtmlBuilder" translates '&' into an entity reference.
This does not follow the DOM spec. It specifies that
character references are expected to be expanded by the
HTML/XML processor.

"XmlWriter/HtmlWriter" does not output the 'amp' entity reference.
This, obviously, is a bug in "XmlWriter/HtmlWriter".
By the way, processing instructions are not output, too.

I have fixed my "&" problem by adding "amp" to the
"expand_entities" tuple in "HtmlBuilde". This, however,
is not a general solution.

- Dieter