gnulib: update to latest upstream revision.

* gnulib: Update.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>

diff --git a/gnulib b/gnulib
index 5191b3546cfb6c163228c23f214e325ddf60d46f..a39d4083cab589d7cd6a13e8a4b8db8875261d75 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 5191b3546cfb6c163228c23f214e325ddf60d46f
+Subproject commit a39d4083cab589d7cd6a13e8a4b8db8875261d75