The answer for gnu readline4.1 + OpenBSD2.8 + PG7.03

Here's what I had to do to get Postgresql 7.03 to detect the gnu
readline lib on OpenBSD 2.8.

1. Install the GNU readline lib.  I got version 4.1, which is
   current.  It installs itself in /usr/local.

2. OpenBSD comes with some readline libs already, but I think these
   are old versions, or they don't work so well, so I got them out of
   the way: mv /usr/include/readline /usr/include/readline.old and mv
   /usr/lib/libreadline.a /usr/lib/libreadline.a.old.

3. ./configure will not detect the new readline stuff in /usr/local/,
   so I had to do ./configure --with-lib=/usr/local/lib
   --with-includes=/usr/local/include.

4. Then make it normally, and everything will work, and you've got
   most up-to-date readline lib.

If you're using Postgres psql without readline support, you should try
to install it because it makes interactive sessions much easier.

Thanks for all the help from the PG list.