Revert "maint: Update to latest gnulib"

Revert @f8172388c which broke the build on Centos 6, because of old
autoconf (< 2.63b) not properly quoting arguments for shell.

diff --git a/.gnulib b/.gnulib
index 47c634c05a946651e2834dcf0cd7cd0dc7a21d3c..ce4ee4cbb596a9d7de2786cf8c48cf62a4edede7 160000 (submodule)
--- a/.gnulib
+++ b/.gnulib
@@ -1 +1 @@
-Subproject commit 47c634c05a946651e2834dcf0cd7cd0dc7a21d3c
+Subproject commit ce4ee4cbb596a9d7de2786cf8c48cf62a4edede7