Resolve "Uncaught TypeError: undefined is not a function" error when both timeout and failure are defined. Fixes #1817 [stanleyhlng]

@tripp 

As per your request on https://github.com/yui/yui3/pull/1818#issuecomment-46490748,  I have created a pull request with src files only against dev-master.

Thank you for your time to review my changes.

Regards,
Stanley