Remove uses of box_syntax in rustc and tools

Author: clubby789

example/alloc_example.rs

@@ -1,4 +1,4 @@
-#![feature(start, box_syntax, core_intrinsics, alloc_error_handler, lang_items)]
+#![feature(start, core_intrinsics, alloc_error_handler, lang_items)]
 #![no_std]
 
 extern crate alloc;
@@ -38,7 +38,7 @@ unsafe extern "C" fn _Unwind_Resume() {
 
 #[start]
 fn main(_argc: isize, _argv: *const *const u8) -> isize {
-    let world: Box<&str> = box "Hello World!\0";
+    let world: Box<&str> = Box::new("Hello World!\0");
     unsafe {
         puts(*world as *const str as *const u8);
     }

example/mini_core_hello_world.rs

@@ -1,7 +1,7 @@
 // Adapted from https://github.com/sunfishcode/mir2cranelift/blob/master/rust-examples/nocore-hello-world.rs
 
 #![feature(
-    no_core, unboxed_closures, start, lang_items, box_syntax, never_type, linkage,
+    no_core, unboxed_closures, start, lang_items, never_type, linkage,
     extern_types, thread_local
 )]
 #![no_core]
@@ -163,7 +163,7 @@ fn main() {
         let ptr: *const u8 = hello as *const [u8] as *const u8;
         puts(ptr);
 
-        let world: Box<&str> = box "World!\0";
+        let world: Box<&str> = Box::new("World!\0");
         puts(*world as *const str as *const u8);
         world as Box<dyn SomeTrait>;
 
@@ -223,10 +223,10 @@ fn main() {
         }
     }
 
-    let _ = box NoisyDrop {
+    let _ = Box::new(NoisyDrop {
         text: "Boxed outer got dropped!\0",
         inner: NoisyDropInner,
-    } as Box<dyn SomeTrait>;
+    }) as Box<dyn SomeTrait>;
 
     const FUNC_REF: Option<fn()> = Some(main);
     #[allow(unreachable_code)]

example/mod_bench.rs

@@ -1,4 +1,4 @@
-#![feature(start, box_syntax, core_intrinsics, lang_items)]
+#![feature(start, core_intrinsics, lang_items)]
 #![no_std]
 
 #[link(name = "c")]