Spell out duplicate hook locations.

props DrewAPicture.
fixes #25658.

Built from https://develop.svn.wordpress.org/trunk@25868


git-svn-id: http://core.svn.wordpress.org/trunk@25780 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/export.php

@@ -367,6 +367,7 @@ function export_wp( $args = array() ) {
 		$is_sticky = is_sticky( $post->ID ) ? 1 : 0;
 ?>
 	<item>
+		<?php /** This filter is documented in wp-includes/feed.php */ ?>
 		<title><?php echo apply_filters( 'the_title_rss', $post->post_title ); ?></title>
 		<link><?php the_permalink_rss() ?></link>
 		<pubDate><?php echo mysql2date( 'D, d M Y H:i:s +0000', get_post_time( 'Y-m-d H:i:s', true ), false ); ?></pubDate>