Bitmap mode and high scaling doesn't render correctly.

[Yazwh0]

This is similar to #433 .

High scaling isn't rendered correctly for bitmaps. Like the tiles we should render colour 0 from the end of the scaled image to the right of the screen.

For V_Scaling, given the screen starts at 0,0, line 480 gets copied from the bottom down to the bottom of the screen.

Example prg and source is attached

Expected (Note the noise at the bottom is random from uninitialised memory)

Current

example.zip
test.txt