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");
}
}
}
[---------------------------------------------------------------------]

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// import Nevow.Athena

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function init() {

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  Nevow.Athena.Widget.fromAthenaID(1).callRemote('HMIexec', 'HMIinitialisation');

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}

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WebInterface.PLC = Nevow.Athena.Widget.subclass('WebInterface.PLC');

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WebInterface.PLC.method(

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	 'updateHMI',

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	 function (self, data) {

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	   d = self.callRemote('getPLCElement');

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	   d.addCallback(

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			 function liveElementReceived(le) {

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				d2 = self.addChildWidgetFromWidgetInfo(le);

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				d2.addCallback(

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						function childAdded(widget) {

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						var node = self.nodeById('content');

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						node.replaceChild(widget.node, node.getElementsByTagName('div')[0]);

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						init();

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						});

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				});

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	   });

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Divmod.Base.addLoadEvent(init);