Adjust configure script to print the bison and flex versions in use.

Minor rearrangements to make a few tests in a more logical order.

configure.in

@@ -1,5 +1,5 @@
 dnl Process this file with autoconf to produce a configure script.
-dnl $PostgreSQL: pgsql/configure.in,v 1.521 2007/07/14 11:13:28 mha Exp $
+dnl $PostgreSQL: pgsql/configure.in,v 1.522 2007/07/19 17:15:30 tgl Exp $
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -650,9 +650,6 @@ AC_MSG_NOTICE([using LDFLAGS=$LDFLAGS])
 
 AC_ARG_VAR(LDFLAGS_SL)
 
-AC_PROG_AWK
-PGAC_PATH_FLEX
-AC_PROG_LN_S
 PGAC_PROG_LD
 AC_SUBST(LD)
 AC_SUBST(with_gnu_ld)
@@ -667,33 +664,14 @@ case $host_os in sysv5*)
   AC_SUBST(ld_R_works)
 esac
 AC_PROG_RANLIB
-AC_PATH_PROG(TAR, tar)
 PGAC_CHECK_STRIP
 
-if test -z "$YACC"; then
-  AC_CHECK_PROGS(YACC, ['bison -y'])
+AC_PATH_PROG(TAR, tar)
+AC_PROG_LN_S
+AC_PROG_AWK
 
-  if test "$YACC"; then
-    if $YACC --version | sed q | $AWK '{ if ($4 < 1.875) exit 0; else exit 1;}'; then
-      AC_MSG_WARN([
-*** The installed version of Bison is too old to use with PostgreSQL.
-*** Bison version 1.875 or later is required.])
-      YACC=""
-    fi
-  fi
-
-  if test -z "$YACC"; then
-    AC_MSG_WARN([
-*** Without Bison you will not be able to build PostgreSQL from CVS nor
-*** change any of the parser definition files.  You can obtain Bison from
-*** a GNU mirror site.  (If you are using the official distribution of
-*** PostgreSQL then you do not need to worry about this, because the Bison
-*** output is pre-generated.)  To use a different yacc program (possible,
-*** but not recommended), set the environment variable YACC before running
-*** 'configure'.])
-  fi
-fi
-AC_SUBST(YFLAGS)
+PGAC_PATH_YACC
+PGAC_PATH_FLEX
 
 PGAC_PATH_PERL
 if test "$with_perl" = yes; then