AHRS: removed constrain() defines

libraries/AP_AHRS/AP_AHRS.cpp

@@ -87,7 +87,6 @@ bool AP_AHRS::airspeed_estimate(float *airspeed_ret)
 		if (_wind_max > 0 && _gps && _gps->status() == GPS::GPS_OK) {
 			// constrain the airspeed by the ground speed
 			// and AHRS_WIND_MAX
-#define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
 			*airspeed_ret = constrain(*airspeed_ret, 
 						  _gps->ground_speed*0.01 - _wind_max, 
 						  _gps->ground_speed*0.01 + _wind_max);

libraries/AP_AHRS/AP_AHRS_DCM.cpp

@@ -18,8 +18,6 @@
 
 extern const AP_HAL::HAL& hal;
 
-#define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
-
 // this is the speed in cm/s above which we first get a yaw lock with
 // the GPS
 #define GPS_SPEED_MIN 300

libraries/AP_AHRS/AP_AHRS_MPU6000.cpp

@@ -122,7 +122,6 @@ void AP_AHRS_MPU6000::drift_correction( float deltat )
         // 0.65*0.04 / 0.005 = 5.2
         float drift_limit = _mpu6000->get_gyro_drift_rate() * deltat 
             / _gyro_bias_from_gravity_gain;
-#define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
         errorRollPitch[0] = constrain(errorRollPitch[0],
                 -drift_limit, drift_limit);
         errorRollPitch[1] = constrain(errorRollPitch[1],