Split tokio-threadpool lib.rs into files (#233)

* Builder -> src/builder.rs
* Callback -> src/callback.rs
* Config -> src/config.rs
* Futures2Wake -> src/futures2_wake.rs
* Inner -> src/inner.rs
* Notifier-> src/notifier.rs
* Sender -> src/sender.rs
* Shutdown -> src/shutdown.rs
* ShutdownTask -> src/shutdown_task.rs
* SleepStack -> src/sleep_stack.rs
* State -> src/state.rs
* ThreadPool -> src/thread_pool.rs
* Worker -> src/worker.rs
* WorkerEntry -> src/worker_entry.rs
* WorkerState -> src/worker_state.rs

tokio-threadpool/src/shutdown_task.rs

@@ -0,0 +1,24 @@
+use futures::task::AtomicTask;
+#[cfg(feature = "unstable-futures")]
+use futures2;
+
+#[derive(Debug)]
+pub(crate) struct ShutdownTask {
+    pub task1: AtomicTask,
+
+    #[cfg(feature = "unstable-futures")]
+    pub task2: futures2::task::AtomicWaker,
+}
+
+impl ShutdownTask {
+    #[cfg(not(feature = "unstable-futures"))]
+    pub fn notify(&self) {
+        self.task1.notify();
+    }
+
+    #[cfg(feature = "unstable-futures")]
+    pub fn notify(&self) {
+        self.task1.notify();
+        self.task2.wake();
+    }
+}