Use newer xfun_handle where

diff --git a/plug b/plug
index c3d0108ef59d40a6079f8da1b7a1c79dc1c80d96..d743d03f8a4c923fd48602455d69bfd7b8d26a46 160000 (submodule)
--- a/plug
+++ b/plug
@@ -1 +1 @@
-Subproject commit c3d0108ef59d40a6079f8da1b7a1c79dc1c80d96
+Subproject commit d743d03f8a4c923fd48602455d69bfd7b8d26a46