AntennaTracker: changes for more common mavlink code
GPS: exclude SIRF and NMEA on APM copter build

This only works for the centralised builder, the modified Arduino IDE
will still include the NMEA and SIRF drivers meaning it will require
approximately 4k additional flash which may push us over the limit on
the APM2.  Users will instead need to exclude other features to get
below the APM1/2 flash limit.
Copter: Acro balance fix
AC_AttitudeControl_Heli: Remove ToDo.  Rate controllers should always run even if throttle is zero.
AP_MotorsHeli: Add To-Do. Swash setup hasn't seemed to work right for a while, this might be why.  Confirm later.
TradHeli: Force recalc scalers after setting main loop time in MotorsHeli so that ramp scalers are right for 32-bit.
Parameters: Update Tune Comments with new options
TradHeli: Move two static bools into heli_flags structure to save 2 bytes RAM.
AC_AttitudeControl: Fixup some minor mistakes in AC_PosControl
build: added some debug
AP_AHRS: Fixed DCM get_gyro function

Previously incorporated the attitude correction terms into the return. Now only returns the drift-corrected gyro.
AP_AHRS_NavEKF: use gyro drift states from EKF in get_gyro
AP_AHRS: fixed gyro_bias sign, and pre-calculate gyro_estimate for EKF

this allows us to return a constant vector for the corrected gyro
estimate. Based on discussions with Jon Challinger
AC_AttitudeControl: Limit _pos_target.z to below alt_max before computing error
INS: calibrated method checks all accelerometers
build: fixed directory handling in build_binaries.sh
AP_Common: added fire cape product ID
AP_InertialSensor_MPU9150: I2C userspace driver sensor added.

The MPU9150 is a 9 axis sensor that includes 3 accelerometers,
3 gyroscopes and 3 magnetometers. All accessible through I2C.
The AP_InertialSensor_MPU9150 class allows APM to use this sensor.
AP_InertialSensor: updates for ERLE board type
HAL_Linux: updates for ERLE board type