Add blank lines after module-level //! comments.

Most modules have such a blank line, but some don't. Inserting the blank
line makes it clearer that the `//!` comments are describing the entire
module, rather than the `use` declaration(s) that immediately follows.

compiler/rustc_middle/src/middle/privacy.rs

@@ -1,6 +1,7 @@
 //! A pass that checks to make sure private fields and methods aren't used
 //! outside their scopes. This pass will also generate a set of exported items
 //! which are available for use externally when compiled as a library.
+
 use crate::ty::{TyCtxt, Visibility};
 use rustc_data_structures::fx::{FxIndexMap, IndexEntry};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};

compiler/rustc_middle/src/ty/abstract_const.rs

@@ -1,4 +1,5 @@
 //! A subset of a mir body used for const evaluability checking.
+
 use crate::ty::{
     self, Const, EarlyBinder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
     TypeVisitableExt,