From: Sam James <sam@gentoo.org>
Date: Wed, 21 Apr 2021 06:20:13 +0100
Subject: Use more modern autoconf archive macro for readline

The previous macro used was pretty obsolete and certainly didn't work
on Gentoo Prefix on Darwin anyway.
--- a/configure.ac
+++ b/configure.ac
@@ -86,19 +86,9 @@ dnl ------------------
 dnl readline detection
 dnl ------------------
 
-abook_cv_readline=/usr
-AC_ARG_WITH(readline, [  --with-readline=DIR     Where readline is installed ],
-	[if test $withval != yes; then
-		abook_cv_readline=$withval
-	fi
-	if test x$abook_cv_readline != x/usr; then
-		LDFLAGS="-L${abook_cv_readline}/lib $LDFLAGS"
-		CPPFLAGS="$CPPFLAGS -I${abook_cv_readline}/include"
-	fi])
-
-AC_LIB_READLINE
-
-if test x$ac_cv_lib_readline = xno -o x$ac_cv_lib_readline_history = xno; then
+AX_LIB_READLINE
+
+if test x$ax_cv_lib_readline = xno -o x$ax_cv_lib_readline_history = xno; then
 	AC_MSG_ERROR([*** readline library not found or it doesn't support history ***])
 fi