Get rid of a couple of copies of the CC0 text. Add header comment to
CC0 files to remind people editing them what the terms are. Also add
some missing XML headers. The header comments in layouts won't bloat
the binary - they get stripped out before compressing, same as any other
comments.
cart slot, added correct keyboard to cpc+ machines (with Fn keys
in place of the keypad number keys), added cpc+ system carts to
the softlist and converted driver to use io_port array for keyboard
input reads. nw.
