TreeWalker implementation

[Richard Moore]

There are some advantages to the XPath implementation Zack and I are working 
on, namely:

- Ease of integration with the rest of kjs/khtml
- Use of dom2 traversal (which will also be available to use directly)
- C++ rather than C and a wrapper
- The code is 

We intend the code to be build on top of the DOM api rather than tying it 
directly to the Qt XML implementation. This would allow us to take advantage 
of any improvements that might be made to the underlying parser etc. 

Implementing progressive building of the DOM tree would be possible in Qt by 
the way if it was constructed using SAX (or even the underlying parser 
implementation).

Cheers

Rich.