Add check bison version in configure.ac file.
To build correctly matiec we need bison greater or equals than 2.4 version.
Now the "configure" script is able to check if system has correctly requirements.
#!/bin/bash
# matiec - a compiler for the programming languages defined in IEC 61131-3
#
# Copyright (C) 2003-2011 Mario de Sousa (msousa@fe.up.pt)
# Copyright (C) 2007-2011 Laurent Bessard and Edouard Tisserant
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
# Shell script to build test for unix likes
STFILE=$1
shift
CFLAGS=$*
CC=gcc
#CC=i686-mingw32-gcc
../iec2c $STFILE -I ../lib
#2>/dev/null
$CC -I ../lib -c STD_RESSOURCE.c $CFLAGS
$CC -I ../lib -c STD_CONF.c $CFLAGS
$CC -I ../lib -c plc.c $CFLAGS
$CC -I ../lib main.c STD_CONF.o STD_RESSOURCE.o plc.o $CFLAGS -l rt -o test