Stabilize #[repr(transparent)]

Tracking issue FCP: https://github.com/rust-lang/rust/issues/43036#issuecomment-394094318
Reference PR: https://github.com/rust-lang-nursery/reference/pull/353

src/test/ui/feature-gate-repr_transparent.rs

@@ -1,14 +0,0 @@
-// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-#[repr(transparent)] //~ error: the `#[repr(transparent)]` attribute is experimental
-struct Foo(u64);
-
-fn main() {}

src/test/ui/feature-gate-repr_transparent.stderr

@@ -1,11 +0,0 @@
-error[E0658]: the `#[repr(transparent)]` attribute is experimental (see issue #43036)
-  --> $DIR/feature-gate-repr_transparent.rs:11:1
-   |
-LL | #[repr(transparent)] //~ error: the `#[repr(transparent)]` attribute is experimental
-   | ^^^^^^^^^^^^^^^^^^^^
-   |
-   = help: add #![feature(repr_transparent)] to the crate attributes to enable
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0658`.

src/test/ui/lint-ctypes.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 #![deny(improper_ctypes)]
-#![feature(libc, repr_transparent)]
+#![feature(libc)]
 
 extern crate libc;