Fix 4.0a baro altitude hung. This is happening when the same port is shared with different devices using a mechanical switch, or a mixer.
What happens is that LK receives a baro altitude, then no more baro, but still keep receiving stuff on the same port.
The UpdateMonitor think that since there is port activity, also baro is still available, and this was wrong.
We now check that the baro altitude is changing if the gps altitude is changing too.
After 1 minute of possible problem, if EnableBaroAltitude is ON, we alert the pilot, we disable baro altitude, and we disable EnableBaroAltitude. If the baro altitude is back available, the pilot must then re-enable its usage with the button.
After 3 times of this problem appearing, we only disable EnableBaroAltitude and we dont reset the baroaltitude anymore, assuming there is a flip/flop condition and a faulty hardware line. Checks after 3 times are delayed to 3 minutes.

Notice: a bluetooth device hanging up, should not be anymore sending anything to LK, and thus the portmonitor should detect the baro altitude missing condition.
	modified:   Comm/UpdateMonitor.cpp