Update to the newest gnulib.

diff --git a/gnulib b/gnulib
index 9f00cc0d8c78cea9e427bb0c40d2ff50d86fe402..5d791c6bbcf2b31b35450bd5a57f45ca66cb532f 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 9f00cc0d8c78cea9e427bb0c40d2ff50d86fe402
+Subproject commit 5d791c6bbcf2b31b35450bd5a57f45ca66cb532f