Add 'feature' and 'since' to stability attributes

src/liballoc/lib.rs

@@ -57,7 +57,7 @@
 //! default global allocator. It is not compatible with the libc allocator API.
 
 #![crate_name = "alloc"]
-#![unstable]
+#![unstable(feature = "unnamed_feature", since = "1.0.0")]
 #![staged_api]
 #![crate_type = "rlib"]
 #![doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",