[sane-devel] genesys backend update

[Stef]

     Hello,

     thanks for an hardware donation from Dany Qumsieh, I have been able 
to work on better support for the LiDE 210. I have improved scanning 
speed at resolution below 600 (saving about 8s), and in the process 
improved darkness issue with this scanner (#313886).
     Incorrect gray scans geometry has also been fixed. However, since 
the motor of the LiDE 100 and 210 can't work at very low resolution, the 
gray scans show some "staircase effect" due to the fact that scan is 
done at a higher resolution, and lines discarded to match the real 
target. I hope to alleviate this by enabling true gray on these sensors.

Regards,
     Stef