the alternatives in a choice node.  The quick checks
  are conservative in the sense that they only detect
  failure with certainty.  Checks can do 2 or 4 characters
  at a time.
* Inline the quick checks to allow the alternatives to
  be checked without branching in the common case where
  they fail.
Review URL: http://codereview.chromium.org/14194

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1005 ce2b1a6d-e550-0410-aec6-3dcde31c8c00