[XML-SIG] gray areas in Python SAX API

[Lars Marius Garshol]

* Alexandre Fayolle
| 
| I've fixed the handlers in dom/ext/reader/Sax2.py and PyExpat.py to work
| properly. The startElement callback was wrong. I've also commited changes
| that enable the xmlns='' attribute to work. 

Excellent!

--Lars M.