Add #[feature(const_mut_refs)] declaration

Nessicarry on current nightly

Author: Techcable

libs/simple/src/lib.rs

@@ -29,8 +29,8 @@
     new_uninit, // Until Rust has const generics, this is how we init arrays..
     ptr_metadata, // Needed to abstract over Sized/unsized types
     // Used for const layout computation:
-    const_raw_ptr_deref,
     const_ptr_offset,
+    const_mut_refs,
     const_align_of_val,
     // Needed for field_offset!
     const_ptr_offset_from,

src/lib.rs

@@ -4,12 +4,12 @@
     unsize,
     trait_alias, // RFC 1733 - Trait aliases
     generic_associated_types, // RFC 1598 - Generic associated types
-    const_raw_ptr_deref, // Needed for const Gc::value
     // Needed for epsilon collector:
     once_cell, // RFC 2788 (Probably will be accepted)
     negative_impls, // More elegant than marker types
     alloc_layout_extra,
     const_fn_fn_ptr_basics,
+    const_mut_refs,
     const_option,
     const_fn_trait_bound, // NOTE: Needed for the `epsilon_static_array` macro
     const_trait_impl, // EXPERIMENTAL: const Deref