Tests for overscan techniques

[larsbrinkhoff]

It's tedious to continuously check that all demos keep working when something in the video components change.

I plan to rip out the juicy bits from various demos, and put them all on a small test floppy. For each technique, display a screen and wait for a key press. The operator would then be able to quickly cycle through all screens and visually confirm they work.

[larsbrinkhoff]

Oh, this is #100. Yay.

[stefanberndtsson]

UGFA.MSA boots directly into a fullscreen thing, so it's a quick test after boot.

[larsbrinkhoff]

I copied some code here:
https://github.com/nocrew/ostis/wiki/Test-cases-from-demos