Update to newest gnulib.

diff --git a/gnulib b/gnulib
index 6909b8edbea806a3bd50aa9baa600cdd3a0a760e..88776ceb6f7a888e2ee6ccf81958a90ec1cee3c2 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 6909b8edbea806a3bd50aa9baa600cdd3a0a760e
+Subproject commit 88776ceb6f7a888e2ee6ccf81958a90ec1cee3c2