AC_AttitudeControl_Heli: Create Flybar Passthrough flag which will be used for control pass-through.
TradHeli: Add pointer for pilot roll/pitch inputs to attitude_control constructor. To be used for flybar passthrough.
AC_AttitudeControl_Heli: Add passthrough_to_motor_roll_pitch function.
AC_AttitudeControl_Heli: Add use_flybar_passthrough accessor function.
TradHeli: Set Flybar passthrough mode in Acro Initialization function.
TradHeli: Reset flybar passthrough to false when exiting Acro mode.
TradHeli: Add yaw-only rate request function for flybar acro mode.
Logging: Fix comment error.
AC_AttControlHeli: add passthrough_bf_roll_pitch_rate_yaw
TradHeli: call passthrough_bf_roll_pitch_rate_yaw
TradHeli: update AttControlHeli constructor

reference to rc_1, rc2 are replaced with constant updates during
acro_run
Rover: show firmware version on param list
Copter: show firmware version on param fetch

fixes pull #1320

thanks Arthur!
AC_AttControl: div-by-zero check for bf-to-ef conversion
AC_AttControlHeli: integrate div-by-zero check for bf-to-ef conversion
Copter: remove get_angle_targets_for_reporting fn

this saves a tiny amount of time by removing the memory copy of a
Vector3f
AC_AttControl: remove debug message
AC_AttControl: bug fix for ef target during acro
AP_NavEKF: make use_compass() public
AP_AHRS: use EKF use_compass() if EKF enabled

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