Remove some unused feature gates

Author: bjorn3

example/arbitrary_self_types_pointers_and_wrappers.rs

@@ -1,7 +1,6 @@
 // Adapted from rustc run-pass test suite
 
 #![feature(arbitrary_self_types, unsize, coerce_unsized, dispatch_from_dyn)]
-#![feature(rustc_attrs)]
 
 use std::{
     ops::{Deref, CoerceUnsized, DispatchFromDyn},

example/mini_core.rs

@@ -1,7 +1,14 @@
 #![feature(
-    no_core, lang_items, intrinsics, unboxed_closures, type_ascription, extern_types,
-    untagged_unions, decl_macro, rustc_attrs, transparent_unions, auto_traits,
-    thread_local,
+    no_core,
+    lang_items,
+    intrinsics,
+    unboxed_closures,
+    extern_types,
+    decl_macro,
+    rustc_attrs,
+    transparent_unions,
+    auto_traits,
+    thread_local
 )]
 #![no_core]
 #![allow(dead_code)]

example/mini_core_hello_world.rs

@@ -7,10 +7,6 @@ extern crate mini_core;
 use mini_core::*;
 use mini_core::libc::*;
 
-unsafe extern "C" fn my_puts(s: *const i8) {
-    puts(s);
-}
-
 macro_rules! assert {
     ($e:expr) => {
         if !$e {