Merge pull request #180 from nrc/rustbuild

Add rustbuild boilerplate

Author: alexcrichton

src/lib.rs

@@ -27,6 +27,9 @@
 //! extern crate rustc_serialize;
 //! ```
 
+#![cfg_attr(rustbuild, feature(staged_api, rustc_private))]
+#![cfg_attr(rustbuild, unstable(feature = "rustc_private", issue = "27812"))]
+
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
        html_favicon_url = "https://www.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/rustc-serialize/")]