Add nested bool to DefKind::Static.

Will be used in the next commit

compiler/rustc_hir/src/def.rs

@@ -78,6 +78,8 @@ pub enum DefKind {
     Static {
         /// Whether it's a `static mut` or just a `static`.
         mt: ast::Mutability,
+        /// Whether it's an anonymous static generated for nested allocations.
+        nested: bool,
     },
     /// Refers to the struct or enum variant's constructor.
     ///