- Verify implementation of nodetest for a named processing instruction.

- Verify that implementation of 'descendant' does not match attribute or
  namespace nodes.

- Verify that the following-sibling and preceding-sibling axis are empty
  for namespace nodes.

- Verify correctness of preceding and following axen.

- Implement functions:
	o id() - this requires access to a document's DTD, to figure out
	  which ID references which node.

- Figure out how nodetests other than * and nodetypes work on the namespace
  axis.

- Augment the function library with ends-with(), min() and max()