Issue #1925738 by tim.plunkett: Followup: Convert language's...

Issue #1925738 by tim.plunkett: Followup: Convert language's system_config_form() to SystemConfigFormBase.

core/modules/language/language.module

@@ -114,14 +114,12 @@ function language_menu() {
   );
   $items['admin/config/regional/language/detection/url'] = array(
     'title' => 'URL language detection configuration',
-    'page callback' => 'NOT_USED',
-    'access arguments' => array('administer languages'),
+    'route_name' => 'language_negotiation_url',
     'type' => MENU_VISIBLE_IN_BREADCRUMB,
   );
   $items['admin/config/regional/language/detection/session'] = array(
     'title' => 'Session language detection configuration',
-    'page callback' => 'NOT_USED',
-    'access arguments' => array('administer languages'),
+    'route_name' => 'language_negotiation_session',
     'type' => MENU_VISIBLE_IN_BREADCRUMB,
   );
   $items['admin/config/regional/language/detection/browser'] = array(
@@ -141,8 +139,7 @@ function language_menu() {
   );
   $items['admin/config/regional/language/detection/selected'] = array(
     'title' => 'Selected language detection configuration',
-    'page callback' => 'NOT_USED',
-    'access arguments' => array('administer languages'),
+    'route_name' => 'language_negotiation_selected',
     'type' => MENU_VISIBLE_IN_BREADCRUMB,
   );