Update to rust master

Author: alexcrichton

tests/smoke.rs

@@ -61,7 +61,7 @@ fn test_rm_tempdir() {
             t!(TempDir::new("test_rm_tempdir"))
         };
         // FIXME(#16640) `: TempDir` annotation shouldn't be necessary
-        let tmp: TempDir = thread::scoped(f).join();
+        let tmp: TempDir = thread::spawn(f).join().unwrap();
         path = tmp.path().to_path_buf();
         assert!(path.exists());
     }
@@ -105,7 +105,7 @@ fn test_rm_tempdir_close() {
             t!(TempDir::new("test_rm_tempdir"))
         };
         // FIXME(#16640) `: TempDir` annotation shouldn't be necessary
-        let tmp: TempDir = thread::scoped(f).join();
+        let tmp: TempDir = thread::spawn(f).join().unwrap();
         path = tmp.path().to_path_buf();
         assert!(path.exists());
         t!(tmp.close());