[9fans] usbhid: usb keyboard/mouse

[Fco.J.Ballesteros <nemo@plan9.escet.urjc.es>]

I've pushed into sources /sys/src/cmd/usb/hid (under /nemo).
It's a usb keyboard / mouse usb driver with some keymaps.
I've been using it for some days with both keyboard&mouse,
and have tested it several times
with just a usb mouse. Although I consider it as beta and will
push (and let you know) a more stable version, I think it can
be used.

It uses the approach suggested by presotto, i.e. it mounts itself
at /dev supplying fake cons/consctl files. This means that
to use it at boot time you'd also need a change in /sys/src/9/boot/boot.c
to start both usbd and usbhid. (and also a change in /lib/namespace
to mount /srv/kfd (besides #c) for programs calling newns).

I'll post all the changes needed after doing more testing and
dismantling the `alternate keyboard driver' (keymaps are
now implemented within usbhid).

hth