Remove conio from the core.

* It is provided by conio.prg, which is loaded at boot time.
Implement tracking of free memory.
Fix memstat and add it to the disk image.
Delete useless filesDelete useless files..
Conio: optimize.

* Let's make this a bit faster...
Use the same shell size as on C64.

* Wide enough to be useful...
Override the CTK service.

* There are some optimizations we can do here by rewriting parts in
assembler. More to come.