BIOS updates

2022-11-16

I worked on the Neotron BIOS interface this week. I merged a bunch of long-standing changes around sharing a VGA-compatible text framebuffer, and added back in Block Device support. I also updated the Neotron Desktop BIOS and the Neotron OS, so you can now get Key Events from the pix-engine GUI window forwarded into the OS via the BIOS HID API.