Update the future/task API

This change updates the future and task API as discussed in the stabilization RFC at https://github.com/rust-lang/rfcs/pull/2592.

Changes:
- Replacing UnsafeWake with RawWaker and RawWakerVtable
- Removal of LocalWaker
- Removal of Arc-based Wake trait

src/libstd/panic.rs

@@ -12,7 +12,7 @@ use panicking;
 use ptr::{Unique, NonNull};
 use rc::Rc;
 use sync::{Arc, Mutex, RwLock, atomic};
-use task::{LocalWaker, Poll};
+use task::{Waker, Poll};
 use thread::Result;
 
 #[stable(feature = "panic_hooks", since = "1.10.0")]
@@ -323,9 +323,9 @@ impl<T: fmt::Debug> fmt::Debug for AssertUnwindSafe<T> {
 impl<'a, F: Future> Future for AssertUnwindSafe<F> {
     type Output = F::Output;
 
-    fn poll(self: Pin<&mut Self>, lw: &LocalWaker) -> Poll<Self::Output> {
+    fn poll(self: Pin<&mut Self>, waker: &Waker) -> Poll<Self::Output> {
         let pinned_field = unsafe { Pin::map_unchecked_mut(self, |x| &mut x.0) };
-        F::poll(pinned_field, lw)
+        F::poll(pinned_field, waker)
     }
 }