serialize: Fully deprecate the library

This commit completes the deprecation story for the in-tree serialization
library. The compiler will now emit a warning whenever it encounters
`deriving(Encodable)` or `deriving(Decodable)`, and the library itself is now
marked `#[unstable]` for when feature staging is enabled.

All users of serialization can migrate to the `rustc-serialize` crate on
crates.io which provides the exact same interface as the libserialize library
in-tree. The new deriving modes are named `RustcEncodable` and `RustcDecodable`
and require `extern crate "rustc-serialize" as rustc_serialize` at the crate
root in order to expand correctly.

To migrate all crates, add the following to your `Cargo.toml`:

    [dependencies]
    rustc-serialize = "0.1.1"

And then add the following to your crate root:

    extern crate "rustc-serialize" as rustc_serialize;

Finally, rename `Encodable` and `Decodable` deriving modes to `RustcEncodable`
and `RustcDecodable`.

[breaking-change]

1 files changed, 5 insertions, 1 deletions

diff --git a/src/libserialize/lib.rs b/src/libserialize/lib.rs
index e700d102fef..7ed806fb3b6 100644
--- a/src/libserialize/lib.rs
+++ b/src/libserialize/lib.rs
@@ -15,7 +15,7 @@ Core encoding and decoding interfaces.
 */
 
 #![crate_name = "serialize"]
-#![experimental]
+#![unstable = "deprecated in favor of rustc-serialize on crates.io"]
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]
 #![doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
@@ -44,3 +44,7 @@ mod collection_impls;
 pub mod base64;
 pub mod hex;
 pub mod json;
+
+mod rustc_serialize {
+    pub use serialize::*;
+}