Include macros from autoconf-archive (pristine)

Reverting this commit should remove the macro code. The project would
still be buildable on any system with autoconf-archive, but since that
is considerably less than systems with autoconf which is our actual
target, we're vendoring a copy of them here. These files should be
bit-for-bit the same as what appears in current macro archives.

build-aux/ax_add_am_macro.m4

@@ -0,0 +1,29 @@
+# ===========================================================================
+#     https://www.gnu.org/software/autoconf-archive/ax_add_am_macro.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_ADD_AM_MACRO([RULE])
+#
+# DESCRIPTION
+#
+#   Adds the specified rule to $AMINCLUDE. This macro will only work
+#   properly with implementations of Make which allow include statements.
+#   See also AX_ADD_AM_MACRO_STATIC.
+#
+# LICENSE
+#
+#   Copyright (c) 2009 Tom Howard <[email protected]>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 10
+
+AC_DEFUN([AX_ADD_AM_MACRO],[
+  AC_REQUIRE([AX_AM_MACROS])
+  AX_APPEND_TO_FILE([$AMINCLUDE],[$1])
+])

build-aux/ax_am_macros.m4

@@ -0,0 +1,44 @@
+# ===========================================================================
+#       https://www.gnu.org/software/autoconf-archive/ax_am_macros.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_AM_MACROS
+#
+# DESCRIPTION
+#
+#   Adds support for macros that create Make rules. You must manually add
+#   the following line
+#
+#     @INC_AMINCLUDE@
+#
+#   to your Makefile.in (or Makefile.am if you use Automake) files.
+#
+# LICENSE
+#
+#   Copyright (c) 2009 Tom Howard <[email protected]>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 11
+
+AC_DEFUN([AX_AM_MACROS],
+[
+AC_MSG_NOTICE([adding automake macro support])
+AMINCLUDE="aminclude.am"
+AC_SUBST(AMINCLUDE)
+AC_MSG_NOTICE([creating $AMINCLUDE])
+AMINCLUDE_TIME=`LC_ALL=C date`
+AX_PRINT_TO_FILE([$AMINCLUDE],[[
+# generated automatically by configure from AX_AUTOMAKE_MACROS
+# on $AMINCLUDE_TIME
+
+]])
+
+INC_AMINCLUDE="include \$(top_builddir)/$AMINCLUDE"
+AC_SUBST(INC_AMINCLUDE)
+])

build-aux/ax_append_to_file.m4

@@ -0,0 +1,27 @@
+# ===========================================================================
+#    https://www.gnu.org/software/autoconf-archive/ax_append_to_file.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_APPEND_TO_FILE([FILE],[DATA])
+#
+# DESCRIPTION
+#
+#   Appends the specified data to the specified file.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Tom Howard <[email protected]>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 9
+
+AC_DEFUN([AX_APPEND_TO_FILE],[
+AC_REQUIRE([AX_FILE_ESCAPES])
+printf "%s" "$2" >> "$1"
+])

build-aux/ax_print_to_file.m4

@@ -0,0 +1,27 @@
+# ===========================================================================
+#     https://www.gnu.org/software/autoconf-archive/ax_print_to_file.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_PRINT_TO_FILE([FILE],[DATA])
+#
+# DESCRIPTION
+#
+#   Writes the specified data to the specified file.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Tom Howard <[email protected]>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 8
+
+AC_DEFUN([AX_PRINT_TO_FILE],[
+AC_REQUIRE([AX_FILE_ESCAPES])
+printf "$2" > "$1"
+])