[request] add a grid overlay when using the full screen scalers

[YaketyJoe]

Is it possible to add a grid overlay (horizontal/vertical lines), to make it look like the original LCD screen? This would be really cool when using the bilinear scaling, and hide the blurriness a bit.

Similar to an LCD shader, but since I know this hardware is very limited, a simple grid overlay might be able to do the job.

[profi200]

To be honest i'm not convinced horizontal lines would look good. The LCDs used on 3DS already have a quite strong line effect and the scaling is not integer so this would be very annoying to get right. Vertical i don't know. It would only really work in 800 pixel mode where we have x3 integer scaling.

I will consider it when i have a proper GPU driver/citro3d port.