tweaks to help C64 kernel start up.
- $D011/$D012 raster register can now be read and returns physical
raster/4
- to help the above, increase frame by 6 rasters to be exactly 4x
PAL frame
- change default screen and border colours so we can see if the
kernel is setting them.
implement raster IRQ in video controller.
fix raster compare register problems, and make rasters triggerable
on any physical raster.