[antlr-interest] added new tree functions

[Terence Parr]

Added cool new methods per earlier discussion

http://www.antlr.org/download/build/antlr-2008-10-22.18.tar.gz

CHANGES

October 22, 2008

* Added inContext() to TreeParser.  Very useful for predicating
   tree grammar productions according to context (their parent list).
   Added new TestTreeContext unit tests (15).

     /** Check if current node in input has a context.  Context means  
sequence
      *  of nodes towards root of tree.  For example, you might say  
context
      *  is "MULT" which means my parent must be MULT.  "CLASS VARDEF"  
says
      *  current node must be child of a VARDEF and whose parent is a  
CLASS node.
      *  You can use "..." to mean zero-or-more nodes.  "METHOD ...  
VARDEF"
      *  means my parent is VARDEF and somewhere above that is a  
METHOD node.
      *  The first node in the context is not necessarily the root.   
The context
      *  matcher stops matching and returns true when it runs out of  
context.
      *  There is no way to force the first node to be the root.
      */
     public boolean inContext(String context) {...}

* Added 3 methods to Tree interface [BREAKS BACKWARD COMPATIBILITY]

     /** Is there is a node above with token type ttype? */
     public boolean hasAncestor(int ttype);

     /** Walk upwards and get first ancestor with this token type. */
     public Tree getAncestor(int ttype);

     /** Return a list of all ancestors of this node.  The first node of
      *  list is the root and the last is the parent of this node.
      */
     public List getAncestors();