- status stay in touching while pen don't realy touch.
- cursor often jumps to center of screen.
But it seems that 'stay in touching' still occurs at rare intervals.
- 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.