maint: simplify updating 'bootstrap' and adjust target 'gnulib-sync'

Copy the 'bootstrap' script from the 'build-aux' directory in gnulib
instead of from the 'top' directory.  The former one already contains
the 'bootstrap-funclib.sh' code which can then be removed as well here.
Finally, remove the obsolete 'autogen.sh' and 'autopull.sh' scripts.

* autogen.sh: Remove.
* autopull.sh: Remove.
* bootstrap-funclib.sh: Remove.
* bootstrap: Update from 'gnulib/build-aux/bootstrap'.
* Makefile.am (gnulib-sync): Change the source dirsctory of 'bootstrap'
from 'top' to 'build-aux', and remove the copying of above obsolete
files.

Makefile.am

@@ -111,12 +111,8 @@ gnulib-sync update-gnulib-to-latest:
 	    && git submodule foreach git pull origin master \
 	    && cp -v gnulib/doc/COPYINGv3 COPYING \
 	    && cp -v gnulib/doc/fdl.texi doc/fdl.texi \
-	    && cp -v gnulib/top/autogen.sh autogen.sh \
-	    && cp -v gnulib/top/autopull.sh autopull.sh \
-	    && cp -v gnulib/top/bootstrap bootstrap \
-	    && cp -v gnulib/top/bootstrap-funclib.sh bootstrap-funclib.sh \
-	    && git status --short -- gnulib COPYING doc/fdl.texi autogen.sh \
-		 autopull.sh bootstrap bootstrap-funclib.sh \
+	    && cp -v gnulib/build-aux/bootstrap bootstrap \
+	    && git status --short -- gnulib COPYING doc/fdl.texi bootstrap \
 	)
 
 # Clean coverage files generated by running binaries built with gcc

autogen.sh

@@ -1,39 +0,0 @@
-#!/bin/sh
-# Convenience script for regenerating all autogeneratable files that are
-# omitted from the version control repository. In particular, this script
-# also regenerates all aclocal.m4, config.h.in, Makefile.in, configure files
-# with new versions of autoconf or automake.
-
-# Copyright (C) 2003-2026 Free Software Foundation, Inc.
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-# Originally written by Paul Eggert.  The canonical version of this
-# script is maintained as top/autogen.sh in gnulib.  However, to be
-# useful to your package, you should place a copy of it under version
-# control in the top-level directory of your package.  The intent is
-# that all customization can be done with a bootstrap.conf file also
-# maintained in your version control; gnulib comes with a template
-# build-aux/bootstrap.conf to get you started.
-#
-# Alternatively, you can use an autogen.sh script that is specific
-# to your package.
-
-me="$0"
-medir=`dirname "$me"`
-
-# Read the function library and the configuration.
-. "$medir"/bootstrap-funclib.sh
-
-autogen "$@"

autopull.sh

@@ -1,37 +0,0 @@
-#!/bin/sh
-# Convenience script for fetching auxiliary files that are omitted from
-# the version control repository of this package.
-
-# Copyright (C) 2003-2026 Free Software Foundation, Inc.
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-# Originally written by Paul Eggert.  The canonical version of this
-# script is maintained as top/autopull.sh in gnulib.  However, to be
-# useful to your package, you should place a copy of it under version
-# control in the top-level directory of your package.  The intent is
-# that all customization can be done with a bootstrap.conf file also
-# maintained in your version control; gnulib comes with a template
-# build-aux/bootstrap.conf to get you started.
-#
-# Alternatively, you can use an autopull.sh script that is specific
-# to your package.
-
-me="$0"
-medir=`dirname "$me"`
-
-# Read the function library and the configuration.
-. "$medir"/bootstrap-funclib.sh
-
-autopull "$@"