[Coco] rgb2vga fix

[Luis Antoniosi (CoCoDemus)]

Hi,

For all trying the rgb2vga I changed the blue resistor, from 390 to 470
ohms. This gives a better blue spectrum. Talking about spectrum, if you
pull the last github files you will notice it's dual clock now. Using
switch FP6 you switch between ntsc clock and pal clock. The pal clock is
needed by the zx-spectrum +2 as it uses a different clock to generate video.



Luis Felipe Antoniosi