gnulib: update

[Akim Demaille]

commit 3c7cc7dc4ff860ec6ba40aa6ed7f2fc85ca22f14
Author: Akim Demaille <akim.demaille@gmail.com>
Date:   Tue Aug 3 07:51:11 2021 +0200

    gnulib: update

diff --git a/gnulib b/gnulib
index 7e3a9c5bd..6dae7213a 160000
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 7e3a9c5bde817dab5b9a6987a373e6a3c2e6576b
+Subproject commit 6dae7213a2e67c0da56f9bb110e2500df4edeeaa
diff --git a/lib/.gitignore b/lib/.gitignore
index 63b3fbc95..c132149fb 100644
--- a/lib/.gitignore
+++ b/lib/.gitignore
@@ -431,7 +431,6 @@
 /unlink.c
 /unlocked-io.h
 /unsetenv.c
-/unused-parameter.h
 /vasnprintf.c
 /vasnprintf.h
 /vasprintf.c
diff --git a/m4/.gitignore b/m4/.gitignore
index 4f0cd4ed1..a7b5095cb 100644
--- a/m4/.gitignore
+++ b/m4/.gitignore
@@ -256,4 +256,5 @@
 /xalloc.m4
 /xsize.m4
 /xstrndup.m4
+/year2038.m4
 /zzgnulib.m4