First steps of &JSRef -> JSRef conversion

Replace &JSRef with JSRef in the bulk of the generated code. This will
remove a level of indirection throughout all DOM code.

This patch doesn't change methods implemented on JSRef<T> to take `self`
rather than `&self`, and it leaves a few other uses of &JSRef, but those
changes can be made incrementally.

components/script/dom/screen.rs

@@ -22,9 +22,9 @@ impl Screen {
         }
     }
 
-    pub fn new(window: &JSRef<Window>) -> Temporary<Screen> {
+    pub fn new(window: JSRef<Window>) -> Temporary<Screen> {
         reflect_dom_object(box Screen::new_inherited(),
-                           &Window(*window),
+                           &Window(window),
                            ScreenBinding::Wrap)
     }
 }