#13 prescale nX filter (decrease blurring)

[Eugene]

When you're using "bilinear filtering" emulator upscale original GB resolution (160x144) to current display resolution, so output image looks too blurry.
Can you add "prescale nX" filter (where "n" is selectable from 1 to 4)
For example, "prescale 2x" filter upscale GB original resolution to 2x (320x288) without interpolation first, and then upscale it to output resolution (what user wants) with bilinear interpolation.

So, when you're increase "n", output image still will look soft, but much less blurry.