Copter: format change to flight mode default defined

This also kicks off the build for AC3.2-rc8
Copter: AC3.2-rc8 release notes
Plane: minor doc update for fence auto enable
HAL_PX4: fixed dirty_mask calculation in FRAM storage

this could lead to a number of bytes on 512 byte boundaries not being
written when changed in ram, so they would revert on next boot
HAL_Linux: fixed storage bug in Linux too
HAL_VRBRAIN: fixed storage bug in VRBRAIN too
Tools/autotest/sim_vehicle.sh: Added option to run the sim_vehicle framework with an external simulator
GCS_MAVLink: mavlink XML updates from upstream
GCS_MAVLink: rebuild MAVLink headers
Copter: AC3.2-rc9 release notes
Copter: remove thr check during init_arm_motors

This check is redundant now that we have a check within the arm_check()
function.
Removing this check does raise a slight danger that someone could raise
the throttle after arming but before the gyro and baro calibration has
completed but the delay has been greatly shortened from what it once was
so there is much less danger that someone could approach the vehicle
during the short arming delay.
Plane: prepare for 3.1.1 release
Plane: improved WP_RADIUS docs