Use key value "ScrollLock" instead of "Scroll"

In the DOM3 Events spec (http://www.w3.org/TR/DOM-Level-3-Events/), there was some confusion as to whether the key value for Scroll Lock should be "Scroll" (as in IE) or "ScrollLock" (which makes more sense). It's been resolved; see https://www.w3.org/Bugs/Public/show_bug.cgi?id=18461.