[Coco] SVGA monitor

[Torsten Dittel]

one reason for better PAL conversion quality might be: the ADC which is 
digitizing the RGB channels (to provide them to the AverLogic (AL25x) 
converter) works somehow better with the lower PAL frequencies. Maybe 
NTSC behaviour could be improved by another external (analog) circuit 
regarding the impedance matching (which might make the PAL quality 
worse, so I'm not really interested in that change, LOL)