allow(deprecated) for TaskPool (fixup #22783)

src/libstd/sync/mod.rs

@@ -31,6 +31,7 @@ pub use self::barrier::{Barrier, BarrierWaitResult};
 pub use self::poison::{PoisonError, TryLockError, TryLockResult, LockResult};
 
 pub use self::future::Future;
+#[allow(deprecated)]
 pub use self::task_pool::TaskPool;
 
 pub mod mpsc;

src/libstd/sync/task_pool.rs

@@ -16,6 +16,8 @@
                         https://crates.io/crates/threadpool")]
 #![unstable(feature = "std_misc")]
 
+#![allow(deprecated)]
+
 use core::prelude::*;
 
 use sync::{Arc, Mutex};