implementation is not yet complete (it prints only the node name for
some AST constructs) and does not serialize everything needed to
reconstitute the AST.

It is motivated by a desire to prototype source-to-source
transformations in JavaScript itself (or anything else that can grok
JSON), but it should have other uses too.

Feedback is welcome.
Review URL: http://codereview.chromium.org/131101

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3051 ce2b1a6d-e550-0410-aec6-3dcde31c8c00