build: update from gnulib, for the lib/*-state.c compilation fixes

* gnulib: Update submodule to latest.

diff --git a/gnulib b/gnulib
index c335e0ec67853b066fae56f6c61b0dbde4c71d74..f56ff6b35bc3869a7d7c4191e06e79c1338caac3 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit c335e0ec67853b066fae56f6c61b0dbde4c71d74
+Subproject commit f56ff6b35bc3869a7d7c4191e06e79c1338caac3