Made more strict by requiring 50 consecutive iterations where the climb
rate is below +- 40cm/s.  Previously it was 50 cumulative.

Removed check of failsafe.radio when clearing the land flag because it
could result in the vehicle taking off if the user picked it up.

thanks to Klrill-ka for the suggestion

fixes issue #1302

This allows a compass that has been declared failed, possibly because of
external disturbances (eg movement of hatches, proximity of tools, etc)
to be given a second chance when the vehicle is armed.

That should be corrected also in MP as the current code is expecting
degrees, not centidegrees.

this provides faster checking of mission waypoints

this ensures we have data for a wide region (1km) around each waypoint

this prevents an old integrator from causing problems on takeoff

this allows magfailed status to show on console via SYS_STATUS health
bits

this allows for testing taildragger takeoffs in FBWA mode

Added Pitch axis flipping. You must be pushing forward or back 3° to make it flip in Pitch axis or it will flip in the default roll axis.
Added some extra throttle control to maintain altitude
removed the CH7 ability to exit Flip mode. It will exit only if completing flip or user aborts with control sticks.

this saves a tiny amount of time by removing the memory copy of a
Vector3f

fixes pull #1320

thanks Arthur!

this is the start of multi-core aware code

this avoids suspending timers when transferring data between main
thread and SPI read thread

reference to rc_1, rc2 are replaced with constant updates during
acro_run

TradHeli: Add pointer for pilot roll/pitch inputs to attitude_control constructor. To be used for flybar passthrough.