rollup merge of #23598: brson/gate

Conflicts:
	src/compiletest/compiletest.rs
	src/libcollections/lib.rs
	src/librustc_back/lib.rs
	src/libserialize/lib.rs
	src/libstd/lib.rs
	src/libtest/lib.rs
	src/test/run-make/rustdoc-default-impl/foo.rs
	src/test/run-pass/env-home-dir.rs

src/libtest/lib.rs

@@ -46,6 +46,7 @@
 #![feature(set_stdio)]
 #![feature(os)]
 #![feature(convert)]
+#![cfg_attr(test, feature(old_io))]
 
 extern crate getopts;
 extern crate serialize;