Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 19743)
+++ wp-includes/functions.php	(working copy)
@@ -517,6 +517,8 @@
 		}
 	}
 
+	$post_links = apply_filters( 'enclosure_links', $post_links );
+
 	foreach ( (array) $post_links as $url ) {
 		if ( $url != '' && !$wpdb->get_var( $wpdb->prepare( "SELECT post_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = 'enclosure' AND meta_value LIKE (%s)", $post_ID, like_escape( $url ) . '%' ) ) ) {