gnulib: Update submodule to recent commit

diff --git a/gnulib b/gnulib
index 29d705ead11382c8d608dcc254394439cb43b9b8..d3efdd55f36a01118ed936da25633858a5757897 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 29d705ead11382c8d608dcc254394439cb43b9b8
+Subproject commit d3efdd55f36a01118ed936da25633858a5757897