- Use CONSOLE_DRIVER() instead of the deprecated CONS_DRIVER() declaration.
- This means we cannot use cn_checkc anymore, which is supposed to do
the same as cn_getc nowadays. Remove the cn_getc implementation (that
was never being called) and rename cn_checkc to cn_getc.
- Don't run-time patch cn_putc, but add the logic to xc_cnputc().
This means I could do some cleanups to our console code...
Tested by: nobody on hackers@