tasks initial impl (still working on task_on trait method)

core/src/widget/handle.rs

@@ -169,3 +169,5 @@ fn null_ptr<W: ?Sized>() -> *const W {
         unsafe { std::mem::transmute_copy(&[0usize; 1]) }
     }
 }
+
+unsafe impl<W: ?Sized> Send for WidgetRef<W> {}