build: update gnulib submodule to latest

* .gnulib: Update to latest.
Commit 89bdf84bcd9c6032e37 inadvertently rewound the .gnulib
submodule by 51 commits.  This corrects it.
Spotted by Eric Blake.

diff --git a/.gnulib b/.gnulib
index 11fbc57405a118e6ec9a3ebc19bbf5ececdae4d6..80cd995cdcbf4b9ded895a43621a11f11806ad8d 160000 (submodule)
--- a/.gnulib
+++ b/.gnulib
@@ -1 +1 @@
-Subproject commit 11fbc57405a118e6ec9a3ebc19bbf5ececdae4d6
+Subproject commit 80cd995cdcbf4b9ded895a43621a11f11806ad8d