gnulib: Update to latest version.

diff --git a/gnulib b/gnulib
index c5c46dcc8e875485a2c5d27cce106491fb41400e..68145a074c0cdc9eff8364a62530da01a5f39bcd 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit c5c46dcc8e875485a2c5d27cce106491fb41400e
+Subproject commit 68145a074c0cdc9eff8364a62530da01a5f39bcd