regular expression match.
Also moves all last-match information into one place where it can be
updated from C++ code (this will be used in another afsnit).
Review URL: http://codereview.chromium.org/28184

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1383 ce2b1a6d-e550-0410-aec6-3dcde31c8c00