bump bootstrap; adjust stage0 uses in core::ptr.

Author: Centril

src/libcore/ptr.rs

@@ -2913,7 +2913,7 @@ impl<T: Sized> NonNull<T> {
     /// some other means.
     #[stable(feature = "nonnull", since = "1.25.0")]
     #[inline]
-    #[cfg_attr(not(stage0), rustc_const_unstable(feature = "const_ptr_nonnull"))]
+    #[rustc_const_unstable(feature = "const_ptr_nonnull")]
     pub const fn dangling() -> Self {
         unsafe {
             let ptr = mem::align_of::<T>() as *mut T;
@@ -2977,7 +2977,7 @@ impl<T: ?Sized> NonNull<T> {
     /// Cast to a pointer of another type
     #[stable(feature = "nonnull_cast", since = "1.27.0")]
     #[inline]
-    #[cfg_attr(not(stage0), rustc_const_unstable(feature = "const_ptr_nonnull"))]
+    #[rustc_const_unstable(feature = "const_ptr_nonnull")]
     pub const fn cast<U>(self) -> NonNull<U> {
         unsafe {
             NonNull::new_unchecked(self.as_ptr() as *mut U)