Use Event._attach to avoid creating unused facades There is a runtime execution and memory cost associated with creating event facades due to the pre-population of e.target, currentTarget, and relatedTarget that can be avoided in this case since it's filtering bubbled mouseover and mouseout events. Create the DOMEventFacade only after passing the filter criteria.

Add lazyEventFacade to YUI config for tests in IE8 This can be removed to do apples-to-apples comparisons with IE6/7/9 for debugging if needed.

Migrate mouseenter to SyntheticEvent infra.

Move manual tests into manual dir manually.