Stabilization for `owned` (now `boxed`) and `cell`

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, 1 insertions, 1 deletions

diff --git a/src/libstd/io/net/unix.rs b/src/libstd/io/net/unix.rs
index c5ddda9945d..5e7c4214977 100644
--- a/src/libstd/io/net/unix.rs
+++ b/src/libstd/io/net/unix.rs
@@ -30,7 +30,7 @@ use c_str::ToCStr;
 use clone::Clone;
 use io::{Listener, Acceptor, Reader, Writer, IoResult, IoError};
 use kinds::Send;
-use owned::Box;
+use boxed::Box;
 use rt::rtio::{IoFactory, LocalIo, RtioUnixListener};
 use rt::rtio::{RtioUnixAcceptor, RtioPipe};