use pregenerated CRC32 lookup tables for retain on Win32 and GNU/Linux

This code could be possible reused on low-end targets with limited RAM.

code to generate lookup table:
[---------------------------------------------------------------------]

/* CRC lookup table and initial state. */
uint32_t crc32_table[256];

/* Generate CRC32 lookup table. */
void GenerateCRC32Table(void)
{
unsigned int i, j;
/* Use CRC-32-IEEE 802.3 polynomial 0x04C11DB7 (bit reflected). */
uint32_t poly = 0xEDB88320;

for (i = 0; i <= 0xFF; i++)
{
uint32_t c = i;
for (j = 0 ; j < 8 ; j++)
c = (c & 1) ? (c >> 1 ) ^ poly : (c >> 1);
crc32_table[i] = c;
}
}

void main(void)
{
GenerateCRC32Table();
int j=0;
for(int i=0; i<256; i++) {
printf("0x%08X, ", crc32_table[i]);
if (++j >= 8) {
j = 0;
printf("\n");
}
}
}
[---------------------------------------------------------------------]

/*

Template C code used to produce target Ethercat C code.

Copyright (C) 2011-2014: Laurent BESSARD, Edouard TISSERANT

Distributed under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

See COPYING file for copyrights details.

*/

#include "iec_types_all.h"

#define FREE 0
#define ACQUIRED 1
#define ANSWERED 2

long SDOLock = FREE;
extern long AtomicCompareExchange(long* atomicvar,long compared, long exchange);

int AcquireSDOLock() {
	return AtomicCompareExchange(&SDOLock, FREE, ACQUIRED) == FREE;
}

void SDOAnswered() {
	AtomicCompareExchange(&SDOLock, ACQUIRED, ANSWERED);
}

int HasAnswer() {
	return SDOLock == ANSWERED;
}

void ReleaseSDOLock() {
	AtomicCompareExchange(&SDOLock, ANSWERED, FREE);
}

int __init_etherlab_ext()
{
    SDOLock = FREE;
    return 0;
}

void __cleanup_etherlab_ext()
{
}

void __retrieve_etherlab_ext()
{
}

void __publish_etherlab_ext()
{
}