Element: Fix signatures of clipboard events

Author: tindzk

src/main/scala/org/scalajs/dom/raw/lib.scala

@@ -777,9 +777,9 @@ abstract class Element
 
   var id: String = js.native
 
-  var oncut: js.Function1[DragEvent, _] = js.native
-  var oncopy: js.Function1[DragEvent, _] = js.native
-  var onpaste: js.Function1[DragEvent, _] = js.native
+  var oncut: js.Function1[ClipboardEvent, _] = js.native
+  var oncopy: js.Function1[ClipboardEvent, _] = js.native
+  var onpaste: js.Function1[ClipboardEvent, _] = js.native
 
   var accessKey: String = js.native