Add missing doc blocks to wp-admin/includes/*.

Fix some egregious uses of tabbing.
Some functions can simply return `apply_filters(...)` instead of setting a variable that is immediately returned.

See #32444.


git-svn-id: https://develop.svn.wordpress.org/trunk@32654 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/widgets.php

@@ -21,6 +21,11 @@ if ( isset($_GET['widgets-access']) ) {
 	set_user_setting( 'widgets_access', $widgets_access );
 }
 
+/**
+ *
+ * @param string $classes
+ * @return string
+ */
 function wp_widgets_access_body_class($classes) {
 	return "$classes widgets_access ";
 }