aix is a Sys V as far as we're concerned.

readline/ChangeLog

@@ -1,3 +1,7 @@
+Thu Oct 24 21:58:46 1991  John Gilmore  (gnu at cygnus.com)
+
+	* configure.in:  aix is a Sys V as far as we're concerned.
+
 Thu Oct 24 02:08:50 1991  Fred Fish  (fnf at cygnus.com)
 
 	* config/hmake-sysv:  Send RANLIB (echo) output to /dev/null.

readline/configure.in

@@ -0,0 +1,17 @@
+# This file is a shell script fragment that supplies the information
+# necessary to tailor a template configure script into the configure
+# script appropriate for this directory.  For more information, check
+# any existing configure script.
+
+configdirs=
+srctrigger=readline.c
+srcname="the readline library"
+
+# per-host:
+
+case "${host_os}" in
+sysv* | irix* | aix*) host_makefile_frag=config/hmake-sysv ;;
+esac
+
+# per-target:
+