OptFlow: fix example sketch so it compiles
Copter: fixed some build warnings
Copter: fence breach causes disarm if landed

Previously it would only disarm if the throttle was also at zero.
Pair programmed with Tridge
Copter: remove unused Log_Write_IMU function
Copter: add DCM_CHECK_THRESH parameter
Copter: add DCM check of yaw error

Triggers an "ekf" failsafe if the DCM yaw error is > 60deg
Copter: enable Optflow by default for Pixhawk only
Copter: fixed parameter path

fixes build of parameters
Copter: support logging while disarmed
Copter: remove extra in_mavlink_delay from should_log function

Also return false when logging disabled
Copter: add NearlyAll-AC315 LOG_BITMASK description
Copter: remove LOG_FROM_STARTUP define

This compile-time method is obsolete now that we have the logging while
disarmed feature
Parachute: set servo or relay to off position on every update

This resolves the issue of the parachute servo's position not being
initialised to the off position due to an ordering problem of the
auxiliary servos being initialised after the parachute object.
Copter: log DCM reported roll-pitch and yaw error
AP_Motors: reduce slow-start increment for fast CPUs
AP_Compass: use apply_correction_function to eliminate duplication
AP_Compass: added some comments
Replay: fixed printf format
AP_Airspeed: fixed airspeed in Replay
Replay: update for new copter ATTITUDE message