Fix fallout in tests.

Author: jseyfried

src/test/compile-fail/auxiliary/issue_12612_1.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(item_like_imports)]
-
 pub mod c {
     pub struct S {}
     pub struct TS();

src/test/compile-fail/auxiliary/namespace-mix-old.rs

@@ -8,19 +8,22 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(rustc_attrs)]
+
 mod foo {
     pub use bar::*;
-    pub use main as f; //~ ERROR has already been imported
+    pub use main as f;
 }
 
 mod bar {
     pub use foo::*;
 }
 
 pub use foo::*;
-pub use baz::*; //~ ERROR has already been imported
+pub use baz::*;
 mod baz {
     pub use super::*;
 }
 
-pub fn main() {}
+#[rustc_error]
+pub fn main() {} //~ ERROR compilation successful