Fix readline/libedit selection code to prefer readline over libedit

reliably (ie, regardless of which libraries they depend on).  Also
make sure that we don't select headers that obviously belong to the
wrong one of the two libraries.  This was discussed back around 4-Sep
but seems to have slipped through the cracks.  The header selection
could be checked more closely, perhaps, but let's see if this is good
enough.

config/programs.m4

-# $PostgreSQL: pgsql/config/programs.m4,v 1.16 2004/09/02 20:39:57 tgl Exp $
+# $PostgreSQL: pgsql/config/programs.m4,v 1.17 2004/11/30 06:13:02 tgl Exp $
 
 
 # PGAC_PATH_FLEX
@@ -82,10 +82,10 @@ AC_MSG_CHECKING([for readline])
 
 AC_CACHE_VAL([pgac_cv_check_readline],
 [pgac_cv_check_readline=no
-for pgac_lib in "" " -ltermcap" " -lncurses" " -lcurses" ; do
-  for pgac_rllib in -lreadline -ledit ; do
-    pgac_save_LIBS=$LIBS
-    LIBS="${pgac_rllib}${pgac_lib} $LIBS"
+pgac_save_LIBS=$LIBS
+for pgac_rllib in -lreadline -ledit ; do
+  for pgac_lib in "" " -ltermcap" " -lncurses" " -lcurses" ; do
+    LIBS="${pgac_rllib}${pgac_lib} $pgac_save_LIBS"
     AC_TRY_LINK_FUNC([readline], [[
       # NetBSD, OpenBSD, and Irix have a broken linker that does not
       # recognize dependent libraries
@@ -99,7 +99,6 @@ for pgac_lib in "" " -ltermcap" " -lncurses" " -lcurses" ; do
       pgac_cv_check_readline="${pgac_rllib}${pgac_lib}"
       break 2
     ]])
-    LIBS=$pgac_save_LIBS
   done
 done
 LIBS=$pgac_save_LIBS

configure.in

 dnl Process this file with autoconf to produce a configure script.
-dnl $PostgreSQL: pgsql/configure.in,v 1.386 2004/11/22 03:06:35 pgsql Exp $
+dnl $PostgreSQL: pgsql/configure.in,v 1.387 2004/11/30 06:13:04 tgl Exp $
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -714,21 +714,34 @@ AC_CHECK_HEADERS(netinet/tcp.h, [], [],
 #endif
 ])
 
-if test "$with_readline" = yes; then
+if expr x"$pgac_cv_check_readline" : 'x-lreadline' >/dev/null ; then
   AC_CHECK_HEADERS(readline/readline.h, [],
-                   [AC_CHECK_HEADERS(editline/readline.h, [],
                    [AC_CHECK_HEADERS(readline.h, [],
                                 [AC_MSG_ERROR([readline header not found
 If you have readline already installed, see config.log for details on the
 failure.  It is possible the compiler isn't looking in the proper directory.
-Use --without-readline to disable readline support.])])])])
+Use --without-readline to disable readline support.])])])
   AC_CHECK_HEADERS(readline/history.h, [],
-                   [AC_CHECK_HEADERS(editline/history.h, [],
                    [AC_CHECK_HEADERS(history.h, [],
                                 [AC_MSG_ERROR([history header not found
 If you have readline already installed, see config.log for details on the
 failure.  It is possible the compiler isn't looking in the proper directory.
-Use --without-readline to disable readline support.])])])])
+Use --without-readline to disable readline support.])])])
+fi
+
+if expr x"$pgac_cv_check_readline" : 'x-ledit' >/dev/null ; then
+  AC_CHECK_HEADERS(editline/readline.h, [],
+                   [AC_CHECK_HEADERS(readline.h, [],
+                                [AC_MSG_ERROR([readline header not found
+If you have libedit already installed, see config.log for details on the
+failure.  It is possible the compiler isn't looking in the proper directory.
+Use --without-readline to disable libedit support.])])])
+  AC_CHECK_HEADERS(editline/history.h, [],
+                   [AC_CHECK_HEADERS(history.h, [],
+                                [AC_MSG_ERROR([history header not found
+If you have libedit already installed, see config.log for details on the
+failure.  It is possible the compiler isn't looking in the proper directory.
+Use --without-readline to disable libedit support.])])])
 fi
 
 if test "$with_zlib" = yes; then