Update to the newest gnulib.

diff --git a/gnulib b/gnulib
index 7d7fd2084fb18f19c8cc79543ed9d73a93984877..dd6b42088bd08c9fdf53ed539c7f50d5009874c1 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 7d7fd2084fb18f19c8cc79543ed9d73a93984877
+Subproject commit dd6b42088bd08c9fdf53ed539c7f50d5009874c1