This is a refactoring-only CL which improves the typing of IDs associated with
AST nodes. The interesting parts are in utils.h and ast.h, the rest of the CL
basically follows mechanically.

Review URL: https://chromiumcodereview.appspot.com/10831172

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12263 ce2b1a6d-e550-0410-aec6-3dcde31c8c00