Justification for the most significant changes:

1.  I added a __setattr__() method to class xml.dom.minidom.Node.  This means existing code that subclasses any of the Node classes *and* overrides __setattr__() *and* isn't calling the base class __setattr__... will not get the new __setattr__ functionality, which basically implements a DOM-compatibility quirk.  I think it's OK.  :)

2.  There's a flag in pyexpat that lets you turn off default attribute values.  The flag is marked "use with caution", because turning this off is not XML-compliant.  expatbuilder was using the flag.  I can't tell why.  There was no comment in the code.  I think it was just a mistake; I changed it, and minidom passes more DOMTS tests as a result.

3.  To implement Attr.specified, I had to expose another Expat API via pyexpat.  This was actually a pretty minor change, but I mention it because I'm sure anyone opening this patch will be shocked that it touches any C code.  :)

4.  Added some big regexes to check for non-XML-compliant names and raise InvalidCharacterErr.  I didn't see a better way to do this.  If anyone is worried about the performance hit from doing these checks, I'll look at it.