reactor: replace ATOMIC_USIZE_INIT with AtomicUsize::new(0) (#889)

ATOMIC_BOOL_INIT is deprecated since 1.34 because the const fn
AtomicUsize::new is now preferred. As deny(warnings) is set,
tokio fails to build on latest nightly. This will fix it.

Signed-off-by: Yilin Chen <[email protected]>

tokio-reactor/src/lib.rs

@@ -71,7 +71,7 @@ use std::io;
 use std::mem;
 use std::cell::RefCell;
 use std::sync::atomic::Ordering::{Relaxed, SeqCst};
-use std::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT};
+use std::sync::atomic::AtomicUsize;
 use std::sync::{Arc, Weak};
 use std::time::{Duration, Instant};
 
@@ -165,7 +165,7 @@ pub(crate) enum Direction {
 }
 
 /// The global fallback reactor.
-static HANDLE_FALLBACK: AtomicUsize = ATOMIC_USIZE_INIT;
+static HANDLE_FALLBACK: AtomicUsize = AtomicUsize::new(0);
 
 /// Tracks the reactor for the current execution context.
 thread_local!(static CURRENT_REACTOR: RefCell<Option<HandlePriv>> = RefCell::new(None));