stabilize atomics (now atomic)

This commit stabilizes the `std::sync::atomics` module, renaming it to
`std::sync::atomic` to match library precedent elsewhere, and tightening
up behavior around incorrect memory ordering annotations.

The vast majority of the module is now `stable`. However, the
`AtomicOption` type has been deprecated, since it is essentially unused
and is not truly a primitive atomic type. It will eventually be replaced
by a higher-level abstraction like MVars.

Due to deprecations, this is a:

[breaking-change]

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libsync/spsc_queue.rs b/src/libsync/spsc_queue.rs
index d8cd44f9935..578e518cb8f 100644
--- a/src/libsync/spsc_queue.rs
+++ b/src/libsync/spsc_queue.rs
@@ -42,7 +42,7 @@ use core::mem;
 use core::cell::UnsafeCell;
 use alloc::arc::Arc;
 
-use atomics::{AtomicPtr, Relaxed, AtomicUint, Acquire, Release};
+use atomic::{AtomicPtr, Relaxed, AtomicUint, Acquire, Release};
 
 // Node within the linked list queue of messages to send
 struct Node<T> {