from devices connected to pckbc:
- Do actual sample collection in pckbc.
- Add rndsource_element_t to the slot data.
- Change pckbc_set_inputhandler() to take an additional argument,
the name of the device, which is (eventually) passed into
rnd_attach_source() to identify the source.
- Change callers of pckbc_set_inputhander() appropriately.
- Wsmouse_input() get new argument 'flag', which indicates whether x/y/z are
relative or absolute.
- Wsmouse get new io controls, WSMOUSEIO_SCALIBCOORDS and
WSMOUSEIO_GCALIBCOORDS.
