auto merge of #15591 : aturon/rust/box-cell-stability, r=alexcrichton

This PR is the outcome of the library stabilization meeting for the
`liballoc::owned` and `libcore::cell` modules.

Aside from the stability attributes, there are a few breaking changes:

* The `owned` modules is now named `boxed`, to better represent its
  contents. (`box` was unavailable, since it's a keyword.) This will
  help avoid the misconception that `Box` plays a special role wrt
  ownership.

* The `AnyOwnExt` extension trait is renamed to `BoxAny`, and its `move`
  method is renamed to `downcast`, in both cases to improve clarity.

* The recently-added `AnySendOwnExt` extension trait is removed; it was
  not being used and is unnecessary.

[breaking-change]

1 files changed, 5 insertions, 2 deletions

diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 1e1522a2bcc..ad6942712ac 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -138,7 +138,7 @@ extern crate rustrt;
 #[cfg(test)] pub use realstd::ops;
 #[cfg(test)] pub use realstd::cmp;
 #[cfg(test)] pub use realstd::ty;
-#[cfg(test)] pub use realstd::owned;
+#[cfg(test)] pub use realstd::boxed;
 #[cfg(test)] pub use realstd::gc;
 
 
@@ -167,7 +167,10 @@ pub use core::unit;
 pub use core::result;
 pub use core::option;
 
-pub use alloc::owned;
+pub use alloc::boxed;
+#[deprecated = "use boxed instead"]
+pub use owned = boxed;
+
 pub use alloc::rc;
 
 pub use core_collections::slice;