Port regexp tests from V8 to Dart.

This adds V8s suite of regular expressions tests. The tests are skipped
for all none d8 runtimes until irregexp has been ported and enabled for
the other runtimes. The tests are enabled when compiling with dart2js
and running with d8.

BUG=http://dartbug.com/21396
R=lrn@google.com

Review URL: https://codereview.chromium.org//667043003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41354 260f80e4-7a28-3924-810f-c04153c831b5