[XML-SIG] pulldom and namespaces

[Martin v. Loewis]

I have updated xml.sax.ContentHandler in PyXML to reflect the API
proposed by Lars, largely by copying Lars' patches for Python 2.  I
have then updated pulldom to use the *NS api. As a result, it now
builds namespacely correct Nodes [I hope]. Please report any problems.

Once Lars has applied his patches to Python 2, these changes to
pulldom need to be merged into Python 2 as well.

Regards,
Martin