Disabling should clear ui-state-hover class

See http://jsfiddle.net/R8xCe/ (click on the button; expected results: class does not include ui-state-hover; actual result: class contains ui-state-hover)

When a button gets disabled, it should not be treated as being hovered upon. In particular, the onmouseout handler no longer is installed so removing your mouse won't remove the hover state, and if you re-enable the button at a later point, it will be spuriously highlighted. This is bad!