gnulib: update to latest

diff --git a/gnulib b/gnulib
index aecd38787af5ca0000e184912194e8c83123eb7f..ffe64673c36168b0e62224429a4870427f2c68c4 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit aecd38787af5ca0000e184912194e8c83123eb7f
+Subproject commit ffe64673c36168b0e62224429a4870427f2c68c4