the averaging array was using 16 bit numbers, but we are storing
numbers with 19 significant bits. That caused overflow at high
altitude, and some very interesting altitude graphs!
Thanks to Michael Oborne for spotting this in a log
* Wire.begin removed from AP_Baro_BMP085::init()
* SPI.begin removed from AP_Baro_MS5611::init()
* SPI.begin removed from AP_InertialSensor_MPU6000::hardware_init()
* Both Wire.begin and SPI.begin added very early in init_ardupilot in
ArduCopter/system.pde and ArduPlane/system.pde