rustdoc: Add a pass to normalize indentation levels in doc comments

src/rustdoc/rustdoc.rs

@@ -102,6 +102,7 @@ fn run(source_file: str) {
         prune_undoc_pass::mk_pass(),
         desc_to_brief_pass::mk_pass(),
         trim_pass::mk_pass(),
+        unindent_pass::mk_pass(),
         markdown_pass::mk_pass {|| std::io:: stdout()}
     ]);
 }