[Tinkerphones] Inferno on Letux 400 Minibook

[David Boddie]

I got SD card writing to work, then I switched out parts of my own
implementation (the SD device file system and the code to expose individual
partitions) in favour of the existing code from the Raspberry Pi port of
Inferno.

I also revisited keyboard handling to prevent hangs that would occur,
hopefully with a more robust implementation that reads the keyboard in the
kernel while handling the keyboard buffer in a daemon.

Now I'm looking at the USB OHCI implementation, taking one from Plan 9 and
trying to make it work.

David