[bug#40033] Add "Vice" commodore emulator

[Christopher Lemmer Webber]

Here's a patch to add the "vice" commodore emulator.  It builds and
works, but has some vices of its own (har har).

 - It ships with the original Kernal/Basic from the c64 (and other
   systems), including the payload for the original Microsoft Basic.
   That's... probably not ok for Guix.

 - One solution is coming out of the Mega65 project (a damn cool project
   in general):
     https://github.com/MEGA65/open-roms
   (Just look how cool the Mega65 hardware is, btw!)
     https://www.youtube.com/watch?v=aEhZfkQ3bAk

 - It really stutters a lot for me.  I don't know why.  I tried turning
   off all the graphical extras and turning on the fastsid audio system
   in the config system and it's still slow.  I can't even run
   robotfindskitten at full speed:
     https://pezi-pink.itch.io/c64-robotfindskitten
   (good FOSS test program, btw.)

Oh well.  What should be done now?  Not sure, and thoughts welcome.

 - Chris

PS: learning 6502 assembly is really fun!  Here's a good resource:
  https://skilldrick.github.io/easy6502/