maint: really do update to latest upstream gnulib

Commit 9a7071e668d044c1c47c855d2f0bc7cadb235071 "maint: update
copyright notices to include 2013." states that this was done, but
it actually was not.

gnulib/: Update to latest upstream.

diff --git a/gnulib b/gnulib
index c3d1ccfdb375b4cb1b912116c084a61422ef47e3..9fc81090f6c5590bd1b0e0fa5087577a2ee43a3e 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit c3d1ccfdb375b4cb1b912116c084a61422ef47e3
+Subproject commit 9fc81090f6c5590bd1b0e0fa5087577a2ee43a3e