Corrected XPath attribute axis specs.
Unfuck XPath axes evaluation.

The evaluation of axes has been fixed by changing the initial context as well as
the behaviour of some of the handler methods.

The initial context has been changed so that it's simply a NodeSet of whatever
the root object is, either a Document or an Element instance. Previously this
would be set to the child nodes of a Document in case the root object was a
Document. This in turn would prevent "child" axes from operating correctly.