Add fetch_nand to atomics

[Mark-Simulacrum]

I think this is all fine but I have little familiarity with the atomic code (or libcore in general) so I may have accidentally done something wrong here...

cc #13226 (the tracking issue)

r? @alexcrichton

[alexcrichton]

@bors: r+

Thanks!

[bors]

📌 Commit 4ef0a4a has been approved by alexcrichton

[kennytm]

@bors r-

Missing #![feature].

[01:20:34]    Compiling std v0.0.0 (file:///checkout/src/libstd)
[01:20:34] error[E0658]: use of unstable library feature 'atomic_nand' (see issue #13226)
[01:20:34]   --> libcore/../libcore/tests/atomic.rs:54:18
[01:20:34]    |
[01:20:34] 54 |     assert_eq!(x.fetch_nand(0x137f, SeqCst), 0xf731);
[01:20:34]    |                  ^^^^^^^^^^
[01:20:34]    |
[01:20:34]    = help: add #![feature(atomic_nand)] to the crate attributes to enable
[01:20:34] 
[01:20:34] error[E0658]: use of unstable library feature 'atomic_nand' (see issue #13226)
[01:20:34]   --> libcore/../libcore/tests/atomic.rs:82:18
[01:20:34]    |
[01:20:34] 82 |     assert_eq!(x.fetch_nand(0x137f, SeqCst), 0xf731);
[01:20:34]    |                  ^^^^^^^^^^
[01:20:34]    |
[01:20:34]    = help: add #![feature(atomic_nand)] to the crate attributes to enable
[01:20:34] 
[01:20:53] error: aborting due to 2 previous errors
[01:20:53] 
[01:20:53] error: Could not compile `core`.

[Mark-Simulacrum]

Waiting on Travis because I suspect that I missed some feature annotations elsewhere as well.

[kennytm]

@bors r=alexcrichton

[bors]

📌 Commit 1335b3d has been approved by alexcrichton