This makes, e.g., Date.parse("2010-08-31T22:35:36-09:00") work as
expected. Without this change, the "-9:00" timezone-offset portion
causes V8 to fail to properly parse that string into a date.
BUG=http://code.google.com/p/v8/issues/detail?id=857
TEST=Try Date.parse("2010-08-31T22:35:36-09:00") and make sure
that it gets parsed without errors and does not return NaN.

Review URL: http://codereview.chromium.org/3318017

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5436 ce2b1a6d-e550-0410-aec6-3dcde31c8c00