i8042 kernel driver should be more robust

[Martin Decky]

The kernel (and possibly also the uspace) i8042 driver should be more robust and deal with unexpected circumstances better.

For example, the routine i8042_clear_buffer() might go into an infinite loop if the i8042 behaves strangely or is not even physically present (but only emulated with the help of the chipset and BIOS, as is the case of many recent USB-only machines).

Also implementing the recommended initialization and self-test sequence of i8042 should help to detect situations where it is better not to deal with the controller at all.