merge revision(s) 4250d7c910fd67c0da07c6213901009330e3cd51,83f96642d2d74569cc38319d02d5922fac8f66b8,447feb0aa08e20cc5eeb8b3a6f881de261a2c9a2,1d80d703141f01383604022f9e8e53e10865197c,e271a3d4afc47e812b50fc9c50f6bf34d2d723a6,366e88e508de7c59d69906ad948cccd7979e932b,d825e34962540d345eb3c5a70eb264b415e915a5,4250d7c910fd67c0da07c6213901009330e3cd51,f9e43782995b1f77e7b10c79941bbbda15620e2a: [Backport #17723]

	autogen.sh: Added

	Currently it just runs "autoreconf --install"
	---
	 aclocal.m4 | 4 ++--
	 autogen.sh | 3 +++
	 2 files changed, 5 insertions(+), 2 deletions(-)
	 create mode 100755 autogen.sh

	autogen.sh: Allow AUTORECONF envvar to specify the autoreconf
	 executable

	---
	 autogen.sh | 2 +-
	 1 file changed, 1 insertion(+), 1 deletion(-)

	Improved autogen.sh

	* update in the source directory
	* make symbolic links instead of copies
	* forward the arguments to autoreconf as-is
	---
	 autogen.sh | 8 +++++++-
	 1 file changed, 7 insertions(+), 1 deletion(-)

	autogen.sh: Make it work with sh (not bash)

	---
	 autogen.sh | 2 +-
	 1 file changed, 1 insertion(+), 1 deletion(-)

	[DOC] Update README files to use autoreconf [ci skip]

	---
	 README.ja.md | 3 +--
	 README.md    | 3 +--
	 2 files changed, 2 insertions(+), 4 deletions(-)

	[DOC] Update README [ci skip]

	* Use `autogen.sh`.
	* The subversion repository is only for old versions, and
	  secondary now.
	* Moved long links to footnotes.
	---
	 README.ja.md | 22 +++++++++-------------
	 README.md    | 11 +++++++----
	 2 files changed, 16 insertions(+), 17 deletions(-)

	Use autogen.sh

	---
	 .github/workflows/baseruby.yml           | 2 +-
	 .github/workflows/check_dependencies.yml | 2 +-
	 .github/workflows/compilers.yml          | 2 +-
	 .github/workflows/macos.yml              | 2 +-
	 .github/workflows/mjit.yml               | 2 +-
	 .github/workflows/ubuntu.yml             | 2 +-
	 6 files changed, 6 insertions(+), 6 deletions(-)

	autogen.sh: Added

	Currently it just runs "autoreconf --install"
	---
	 aclocal.m4 | 4 ++--
	 autogen.sh | 3 +++
	 2 files changed, 5 insertions(+), 2 deletions(-)
	 create mode 100755 autogen.sh

	get rid of aclocal (#4280)

	---
	 aclocal.m4   | 47 -----------------------------------------------
	 configure.ac | 35 ++++++++++++++++++++++++++++++++++-
	 2 files changed, 34 insertions(+), 48 deletions(-)

1 files changed, 0 insertions, 48 deletions

diff --git a/aclocal.m4 b/aclocal.m4
index 940d91e83f..e69de29bb2 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -1,48 +0,0 @@
-# generated automatically by aclocal 1.16.2 -*- Autoconf -*-
-
-# Copyright (C) 1996-2020 Free Software Foundation, Inc.
-
-# This file is free software; the Free Software Foundation
-# gives unlimited permission to copy and/or distribute it,
-# with or without modifications, as long as this notice is preserved.
-
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY, to the extent permitted by law; without
-# even the implied warranty of MERCHANTABILITY or FITNESS FOR A
-# PARTICULAR PURPOSE.
-
-m4_ifndef([AC_CONFIG_MACRO_DIRS], [m4_defun([_AM_CONFIG_MACRO_DIRS], [])m4_defun([AC_CONFIG_MACRO_DIRS], [_AM_CONFIG_MACRO_DIRS($@)])])
-m4_include([tool/m4/_colorize_result_prepare.m4])
-m4_include([tool/m4/ac_msg_result.m4])
-m4_include([tool/m4/colorize_result.m4])
-m4_include([tool/m4/ruby_append_option.m4])
-m4_include([tool/m4/ruby_append_options.m4])
-m4_include([tool/m4/ruby_check_builtin_func.m4])
-m4_include([tool/m4/ruby_check_builtin_setjmp.m4])
-m4_include([tool/m4/ruby_check_printf_prefix.m4])
-m4_include([tool/m4/ruby_check_setjmp.m4])
-m4_include([tool/m4/ruby_check_signedness.m4])
-m4_include([tool/m4/ruby_check_sizeof.m4])
-m4_include([tool/m4/ruby_check_sysconf.m4])
-m4_include([tool/m4/ruby_cppoutfile.m4])
-m4_include([tool/m4/ruby_decl_attribute.m4])
-m4_include([tool/m4/ruby_default_arch.m4])
-m4_include([tool/m4/ruby_define_if.m4])
-m4_include([tool/m4/ruby_defint.m4])
-m4_include([tool/m4/ruby_dtrace_available.m4])
-m4_include([tool/m4/ruby_dtrace_postprocess.m4])
-m4_include([tool/m4/ruby_func_attribute.m4])
-m4_include([tool/m4/ruby_mingw32.m4])
-m4_include([tool/m4/ruby_prepend_option.m4])
-m4_include([tool/m4/ruby_prog_gnu_ld.m4])
-m4_include([tool/m4/ruby_replace_funcs.m4])
-m4_include([tool/m4/ruby_replace_type.m4])
-m4_include([tool/m4/ruby_rm_recursive.m4])
-m4_include([tool/m4/ruby_setjmp_type.m4])
-m4_include([tool/m4/ruby_stack_grow_direction.m4])
-m4_include([tool/m4/ruby_try_cflags.m4])
-m4_include([tool/m4/ruby_try_cxxflags.m4])
-m4_include([tool/m4/ruby_try_ldflags.m4])
-m4_include([tool/m4/ruby_type_attribute.m4])
-m4_include([tool/m4/ruby_universal_arch.m4])
-m4_include([tool/m4/ruby_werror_flag.m4])