gnulib: Update submodule

diff --git a/gnulib b/gnulib
index 722f67e9716bf914c18d468336c1f4f9e5cce915..491f1bb7d3049f3ab7825f3ee665c209658e9965 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 722f67e9716bf914c18d468336c1f4f9e5cce915
+Subproject commit 491f1bb7d3049f3ab7825f3ee665c209658e9965