Update to newest gnulib.

diff --git a/gnulib b/gnulib
index 5e50baa16ef90204d9048a9e2f23c5a538955121..564afbf88812844f83589d091bff88af55556de6 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 5e50baa16ef90204d9048a9e2f23c5a538955121
+Subproject commit 564afbf88812844f83589d091bff88af55556de6