Update runtime files
diff --git a/src/xdiff/README.txt b/src/xdiff/README.txt
index 95b2242..9e01a3c 100644
--- a/src/xdiff/README.txt
+++ b/src/xdiff/README.txt
@@ -13,4 +13,7 @@
 
 Changes in these files were made to avoid compiler warnings.
 
+The /* */ comments are kept to make syncing to a newer version easier, do not
+change them to // comments!
+
 The first work for including xdiff in Vim was done by Christian Brabandt.