Generate docs for links to private items when passed --document-private

- Pass around document_private a lot more
- Add tests
  + Add tests for intra-doc links to private items
  + Add ignored tests for warnings in reference links

src/librustdoc/config.rs

@@ -123,10 +123,6 @@ pub struct Options {
     ///
     /// Be aware: This option can come both from the CLI and from crate attributes!
     pub default_passes: DefaultPassOption,
-    /// Document items that have lower than `pub` visibility.
-    pub document_private: bool,
-    /// Document items that have `doc(hidden)`.
-    pub document_hidden: bool,
     /// Any passes manually selected by the user.
     ///
     /// Be aware: This option can come both from the CLI and from crate attributes!
@@ -177,8 +173,6 @@ impl fmt::Debug for Options {
             .field("test_args", &self.test_args)
             .field("persist_doctests", &self.persist_doctests)
             .field("default_passes", &self.default_passes)
-            .field("document_private", &self.document_private)
-            .field("document_hidden", &self.document_hidden)
             .field("manual_passes", &self.manual_passes)
             .field("display_warnings", &self.display_warnings)
             .field("show_coverage", &self.show_coverage)
@@ -250,6 +244,10 @@ pub struct RenderOptions {
     pub generate_search_filter: bool,
     /// Option (disabled by default) to generate files used by RLS and some other tools.
     pub generate_redirect_pages: bool,
+    /// Document items that have lower than `pub` visibility.
+    pub document_private: bool,
+    /// Document items that have `doc(hidden)`.
+    pub document_hidden: bool,
 }
 
 impl Options {
@@ -567,8 +565,6 @@ impl Options {
             should_test,
             test_args,
             default_passes,
-            document_private,
-            document_hidden,
             manual_passes,
             display_warnings,
             show_coverage,
@@ -597,6 +593,8 @@ impl Options {
                 markdown_playground_url,
                 generate_search_filter,
                 generate_redirect_pages,
+                document_private,
+                document_hidden,
             },
             output_format,
         })