let's not touch leds from interrupt handler, somewhat
board specific, too.
left-over MD bits possibly harmful for non-cubieboard sunxis.
stdbool is not needed in C, however is need for c++

Suggested by patrick@

ok marco@ pedro@, with grudging approval by oga@
Clear SENSOR_FINVALID to stop sensors from disappearing permanently.

input and ok patrick@
ok oga@
Don't populate absent sensors with bogus values.

ok oga@ patrick@