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/mpsc_queue.rs b/src/libsync/mpsc_queue.rs
index 4f5dd07a6e5..012574808f3 100644
--- a/src/libsync/mpsc_queue.rs
+++ b/src/libsync/mpsc_queue.rs
@@ -46,7 +46,7 @@ use alloc::boxed::Box;
 use core::mem;
 use core::cell::UnsafeCell;
 
-use atomics::{AtomicPtr, Release, Acquire, AcqRel, Relaxed};
+use atomic::{AtomicPtr, Release, Acquire, AcqRel, Relaxed};
 
 /// A result of the `pop` function.
 pub enum PopResult<T> {