Update to the newest gnulib.

diff --git a/gnulib b/gnulib
index 75541c6adaf6fc45541a35d2c8803b9b68f2a7fc..6ef3d783333346333f35bb181ba90f5bc46c0b29 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 75541c6adaf6fc45541a35d2c8803b9b68f2a7fc
+Subproject commit 6ef3d783333346333f35bb181ba90f5bc46c0b29