gnulib: update

This addresses a suggestion Bruno Haible made several months ago.

commit 27f0d5a1671896f0e9b5fe5a96acdf4119ea7f36
Author: Akim Demaille <[email protected]>
Date:   Sun Nov 29 17:20:53 2020 +0100

    gnulib: update

diff --git a/Makefile.am b/Makefile.am
index e0aa88af..e5998639 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -78,7 +78,8 @@ clean-local:
 
 .PHONY: gitsort
 gitsort:
-	cd $(srcdir) && for i in $$(git ls-files '*.gitignore'); do	\
+	cd $(srcdir)							\
+	&& for i in $$(git ls-files '*.gitignore' | grep -v doc); do	\
 	  LC_ALL=C sort $$i -o $$i;					\
 	done
 
diff --git a/TODO b/TODO
index 3202d96b..875de655 100644
--- a/TODO
+++ b/TODO
@@ -9,14 +9,6 @@ And add tests in calc.at, to prepare work for D.
 ** YYERROR and yynerrs
 We are missing some cases.  Write a test case, and check all the skeletons.
 
-** gnulib
-Bruno notes:
-
-> I haven't looked deeply, but it strikes me that gnulib/lib/bitset/array.c
-> does not make use of the 'ffsl' function, nor or the 'integer_length_l'
-> function. Maybe because in Bison, all bitsets are so dense that it does
-> not give a performance advantage?
-
 ** Cex
 *** Improve gnulib
 Don't do this (counterexample.c):
diff --git a/bootstrap b/bootstrap
index 8f76d696..5f1b1b70 100755
--- a/bootstrap
+++ b/bootstrap
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Print a version string.
-scriptversion=2020-04-13.15; # UTC
+scriptversion=2020-11-18.17; # UTC
 
 # Bootstrap this package from checked-out sources.
 
@@ -71,7 +71,9 @@ Options:
  --no-git                 do not use git to update gnulib.  Requires that
                           --gnulib-srcdir point to a correct gnulib snapshot
  --skip-po                do not download po files
-
+EOF
+  bootstrap_print_option_usage_hook
+  cat <<EOF
 If the file $me.conf exists in the same directory as this script, its
 contents are read as shell variables to configure the bootstrap.
 
@@ -154,6 +156,18 @@ gnulib_files=
 : ${AUTOPOINT=autopoint}
 : ${AUTORECONF=autoreconf}
 
+# A function to be called for each unrecognized option.  Returns 0 if
+# the option in $1 has been processed by the function.  Returns 1 if
+# the option has not been processed by the function.  Override it via
+# your own definition in bootstrap.conf
+
+bootstrap_option_hook() { return 1; }
+
+# A function to be called in order to print the --help information
+# corresponding to user-defined command-line options.
+
+bootstrap_print_option_usage_hook() { :; }
+
 # A function to be called right after gnulib-tool is run.
 # Override it via your own definition in bootstrap.conf.
 bootstrap_post_import_hook() { :; }
@@ -335,7 +349,7 @@ do
   --no-git)
     use_git=false;;
   *)
-    die "$option: unknown option";;
+    bootstrap_option_hook $option || die "$option: unknown option";;
   esac
 done
 
diff --git a/gnulib b/gnulib
index 9351b403..b141afaf 160000
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 9351b4033bbf0bb1df3d3412376fefe785168c27
+Subproject commit b141afaf9ba197e361510da075556822ac453ff6
diff --git a/lib/.gitignore b/lib/.gitignore
index b927d8e0..877ef777 100644
--- a/lib/.gitignore
+++ b/lib/.gitignore
@@ -173,6 +173,9 @@
 /iconv_open-zos.gperf
 /iconv_open-zos.h
 /iconv_open.c
+/integer_length.c
+/integer_length.h
+/integer_length_l.c
 /intprops.h
 /inttypes.h
 /inttypes.in.h
@@ -379,7 +382,6 @@
 /vfprintf.c
 /vsnprintf.c
 /vsprintf.c
-/w32spawn.h
 /wait-process.c
 /wait-process.h
 /waitpid.c
@@ -399,6 +401,8 @@
 /windows-recmutex.h
 /windows-rwlock.c
 /windows-rwlock.h
+/windows-spawn.c
+/windows-spawn.h
 /windows-tls.c
 /windows-tls.h
 /xalloc-die.c