Plane: prevent integer underflow with comm_get_txspace()
GCS_MAVLink: prevent integer underflow with comm_get_txspace()
autotest: use run_in_terminal.sh for HIL
Rover: avoid integer underflow in mavlink txspace check
Copter: avoid integer underflow in mavlink txspace check
FollowMe: avoid integer underflow in mavlink txspace check
AntennaTracker: avoid integer underflow in mavlink txspace check
AP_InertialSensor: avoid integer underflow in mavlink txspace check
GCS_MAVLink: avoid integer underflow in mavlink txspace check
Rover: change default throttle slew rate to 100

this will help with NiMH batteries which may brownout with sudden
currents
Baro_Glitch: initial version of baro glitch protection

Based on GPS Glitch protection library
Notify: add baro_glitch flag
InertialNav: skip baro updates when glitching

Also resets inertial nav alt estimate once glitch clears
INav_EKF: accept baro_glitch in constructor

Required so it can create an InertialNav object
Copter: integrate baro glitch protection
SITL: add ACC_BIAS and BARO_GLITCH parameters

These allow testing accelerometer bias which often comes from vibration
and sudden changes in baro altitude.
HAL_AVR_SITL: integrate ACC_BIAS and BARO_GLITCH

Adjust simulated accelerometer values and barometer altitude
Notify: RGB led flashes yellow-purple for baro warning
Notify: baro warning tone alarm
Notify: APM2 buzzer for arming, ekf and baro failures