rustdoc: Filter out private definitions. Closes #3538

Author: z0w0

src/librustdoc/rustdoc.rc

@@ -116,8 +116,7 @@ fn run(config: Config) {
             // Remove things marked doc(hidden)
             prune_hidden_pass::mk_pass(),
             // Remove things that are private
-            // XXX enable this after 'export' is removed in favor of 'pub'
-            // prune_private_pass::mk_pass(),
+            prune_private_pass::mk_pass(),
             // Extract brief documentation from the full descriptions
             desc_to_brief_pass::mk_pass(),
             // Massage the text to remove extra indentation