o Only substitute constant values for full-words and not for
   accidental partial matches.

 o Keep the order of macros as in macros.py and allow depending on the
   previous macros.  We used to allow depending on macros that
   happened to sort after the current one in the dictionary.

Review URL: http://codereview.chromium.org/2800042

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5022 ce2b1a6d-e550-0410-aec6-3dcde31c8c00