The VIC-I draws a fixed 22x23 character window, centered in the picture.
The emulator used the VIC-II's display window registers, so the window was
placed at a garbage offset: the first character column was clipped in half
and the whole picture was shifted 24 pixels to the right to hide it.
- the new emulator core (chips) centers the window and takes its vertical
position from the ROM, so NTSC and PAL ROMs both work
- the 24 pixel video shift is gone
- the platform loads res/vic20/vic20.bios (a real ROM set) when it is
available, and falls back to the stub BIOS otherwise
- a regression test checks the geometry of the rendered frame
Steven Hugg