Update to newest gnulib.

diff --git a/gnulib b/gnulib
index ab5b2560b129ae8dc939d79d0be4af6b5ec46885..d617a4bb9b2373961e2e605b78bd3dac346494be 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit ab5b2560b129ae8dc939d79d0be4af6b5ec46885
+Subproject commit d617a4bb9b2373961e2e605b78bd3dac346494be