rollup merge of #20708: aturon/new-int-modules

Conflicts:
	src/libserialize/lib.rs

src/libserialize/lib.rs

@@ -24,8 +24,9 @@ Core encoding and decoding interfaces.
        html_root_url = "http://doc.rust-lang.org/nightly/",
        html_playground_url = "http://play.rust-lang.org/")]
 #![allow(unknown_features)]
-#![feature(slicing_syntax)]
 #![cfg_attr(stage0, allow(unused_attributes))]
+#![feature(old_impl_check)]
+#![feature(slicing_syntax)]
 
 // test harness access
 #[cfg(test)] extern crate test;