- rc_override_active is never set anywhere in the ArduPlane code; it's only used for Copter and Rover. Removing it significantly simplifies the failsafe code.
- modified code has been tested in SITL. Heartbeat and RC failures in AUTO, CRUISE, and RTL modes (covering the three cases in the failsafe check functions) have been simulated with FS_LONG_ACTN = 0, 1, and 2, FS_SHORT_ACTN = 0, 1, and 2, and FS_GCS_ENABL = 0, 1, and 2. In all cases the results are identical to those with the original code.

As suggested in the thread at the following link:
https://groups.google.com/forum/#!topic/drones-discuss/hiD23c3w6xQ

(Plane Only) If the yaw and GPS heading disagree by more than 45 degrees on takeoff, then the magnetometer is declared as failed. The heading is then reset based on the difference between GPS ground track and stgate velocity vector.
Magnetometer fusion uses corrected data and bias states are initialised to zero. This allows the compass to be switched in flight.
For persistent compass errors that trigger a timeout, the compass is not permanently failed, however for non-forward fly vehicles the compass weighting is reduced.

exit from the autpilot when reboot is commanded.
The software assumes that the code is being
launched in an infinite loop thereby an exit
will make it reboot.

Preliminary support for Zynq/Linux on the 'ZyboPilot' HW platform.

see https://github.com/trjw/ZyboPilot-bsp

 for the PetaLinux / Vivado project
files.

At this stage CPPM/Pulse in and PWM out work, and in CLI mode the passthru
test works correctly.

The platform has passed minimal smoke testing in HIL mode.

ZYNQ IS NOT FLIGHT TESTED YET!  FLY THIS PLATFORM AT YOUR OWN RISK!

Signed-off-by: John Williams <john@whelanwilliams.net>

too many people are still not tuning. At least this will give them a
chance to get their aircraft back in a cross-wind

allows airspeed calibration to be skipped for easier startup

makes it more obvious where the build ends up

this creates a core file

try to catch floating pt exception causes

this will allow users to disable it if it proves to be a problem with
no airspeed sensor

fixes issue #1555