[antlr-interest] tree interpreters and node streams

[Terence Parr]

Hi,

Just made some big changes in the tree node stream stuff to support  
interpreters.The issue was that the current tree nodes stream did not  
buffer any node pointers so it was not really suited for  
interpreters, which need to jump around in the treenode stream quite  
a bit. When building the buffered version, I noticed that it was much  
simpler and faster than the unbuffered version so I have made it the  
common treenode stream.  It has extra methods for push and pop of  
indexes so that you can make an interpreter that jumps around. I've  
re-factored the unit tests for treenode stream and added a few tests  
for the push and pop.

Also, importantly, made CommonTreeNodeStream work with any tree node  
type. It assumes object now and uses an adapter.

* New CommonTreeNodeStream buffers all nodes in stream for fast jumping
   around.  It now has push/pop methods to invoke other locations in
   the stream for building interpreters.

* Moved CommonTreeNodeStream to UnBufferedTreeNodeStream and removed
   Iterator implementation.  moved toNodesOnlyString() to  
TestTreeNodeStream

* [BREAKS ANY TREE IMPLEMENTATION]
   made CommonTreeNodeStream work with any tree node type.  TreeAdaptor
   now implements isNil so must add; trivial, but does break back
   compatibility.

Okay, back to writing the book. Finished tree construction, tree  
parsing chapters.  Now templates, error reporting, intro and I'm done!

Ter