[sane-devel] gt68xx backend update

[stef]

	Hello,

	I have added the Iriscan Express 2 to the supported models of the gt68xx 
backend based on the various reports that reached sane-devel list. It would be 
nice if latest sources in the git repository could be tested regarding this 
change.

	I have also fixed the y positioning bug that affected sheetfed scanners by 
implementing the '0x82 request' that moves the document by the y distance 
provided. This request is now used for sheetfed scanners since the 'move 
before scan' values are ignored in effective scans for these models.

	Work on calibration is progressing nicely, I have already have it working. I 
need to do extensive tests and add calibration persistence in file before 
committing it.

Regards,
	Stef