Ignore test262 data files downloaded by test harness.

R=jkummerow@chromium.org
Review by mail to v8-dev@googlegroups.com list.


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14878 ce2b1a6d-e550-0410-aec6-3dcde31c8c00