1) Complete CoreXPath2ParserVisitor which does Normalization to XPath2 Core.
2) Work on XPath2Core.jjt.  How can we do this to maximize reuse with
   XPath2.jjt?  The grammars are very similar in certain regards.
3) XPath2ParserTest needs work.  The test data should be externalized to XML.
   The test case name is misleading, as it is in reality a whole series of
   tests run in coordination, not just for XPath2Parser.
4) The formal semantics spec says that Static Context Processing is input into
   the Normalization phase.  It's not clear where this is actually needed
   during Normalization.  I must have overlooked something.
5) Once we have an XPath2 Core AST available, work can start upon the Static
   type analysis, and ultimately the Dynamic Evaluation Phase (DEP).
6) Need to get the XPath Data Model (XDM) figured out, and how that integrates
   into the DEP.