Vertical scaling support added

[mar753]

I have added vertical scaling support (SCALER_CTL), this fixes the issue e.g. in Crazy Taxi pause screen, where background is not properly aligned (see the red arrow):

[skmp]

@mar753 can't the fraction be calculated like 0x0400/(float)0x0400?

[skmp]

(Sorry for the late review, been busy irl)

[mar753]

First stage here is to convert binary fraction coded number (which Dreamcast is using in this case) to IEEE 754 - I have used double for better precision, which can make a difference here (binaryFractionToDouble() function). Second stage is to multiply current screen height by this factor, round is necessary to be used here, because ceil/floor or simple division are not sufficient here and may generate +/- 1px or more uncertainty. I have tested it very carefully with different games and rounding the final double number only, does generate graphics exactly like on Dreamcast, without any stretching, with the picture covering the whole screen.