match.  Sometimes were were not updating it when we should
and sometimes we were leaving the lastMatchInfoOverride in
place when we should be using the updated regular last match
info.  Small optimization for zero length match in
String.prototype.replace.
Review URL: https://chromiumcodereview.appspot.com/10184004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11422 ce2b1a6d-e550-0410-aec6-3dcde31c8c00