std: Enable usage of thread_local! through imports

The `thread_local!` macro delegated to an internal macro but it didn't
do so in a macros-and-the-module-system compatible fashion, meaning if a
`#![no_std]` crate imported `std` and tried to use `thread_local!` it
would fail due to missing a lookup of an internal macro.

This commit switches the macro to instead use `$crate` to invoke other
macros, ensuring that it'll work when `thread_local!` is imported alone.

src/libstd/thread/local.rs

@@ -145,13 +145,13 @@ macro_rules! thread_local {
 
     // process multiple declarations
     ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr; $($rest:tt)*) => (
-        __thread_local_inner!($(#[$attr])* $vis $name, $t, $init);
-        thread_local!($($rest)*);
+        $crate::__thread_local_inner!($(#[$attr])* $vis $name, $t, $init);
+        $crate::thread_local!($($rest)*);
     );
 
     // handle a single declaration
     ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr) => (
-        __thread_local_inner!($(#[$attr])* $vis $name, $t, $init);
+        $crate::__thread_local_inner!($(#[$attr])* $vis $name, $t, $init);
     );
 }
 
@@ -201,7 +201,7 @@ macro_rules! __thread_local_inner {
     };
     ($(#[$attr:meta])* $vis:vis $name:ident, $t:ty, $init:expr) => {
         $(#[$attr])* $vis const $name: $crate::thread::LocalKey<$t> =
-            __thread_local_inner!(@key $(#[$attr])* $vis $name, $t, $init);
+            $crate::__thread_local_inner!(@key $(#[$attr])* $vis $name, $t, $init);
     }
 }
 

src/test/run-pass/thread-local-not-in-prelude.rs

@@ -0,0 +1,18 @@
+// Copyright 2018 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.
+
+#![no_std]
+
+extern crate std;
+
+std::thread_local!(static A: usize = 30);
+
+fn main() {
+}