xdiff/xprepare: improve O(n*m) performance in xdl_cleanup_records()

diff --git a/RelNotes b/RelNotes
index 03c996d22ac5e007157998aba981ab113cf1ad7c..6372427426d80b01b03437fd1a55fd412fb8f75d 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.6.3.4.txt
\ No newline at end of file
+Documentation/RelNotes/1.7.7.txt
\ No newline at end of file