PIOS Sensors: Create a general sensors interface
Sensors: get freedom using the new sensor queues for mpu6000
PiOS HMC5883: Create a task to get the mag data.  This is because these
methods should not be called from userspace
Sensors: Reenable mag calibration
Merge branch 'next' into general_sensors

Conflicts:
	flight/Modules/Sensors/sensors.c
Sensors: Get MS5611 registering against the general sensor interface
PIOS MPU6000: Changes to the startup code
PiOS MS5611: Make the device handle static
PiOS MS5611: Now the driver doesn't export the GetTemperature / GetPressure
methods they aren't required since they just add more checks on the device
handle for no reason
PIOS MPU6000: Move the configured flag into the device structure
Add PIOS_SENSORS to all the targets
PiOS L3GD20: Update to the new sensor API.  Remove functions from the public
API that should no longer go there and make others static.
PiOS LSM303: Update to the new sensor API and remove public facing API
that should no longer be exported.
PiOS LSM303: When the data ready semaphore expires then kickstart the
sensor (used to be in the attitude task).
PIOS HMC5883: Make sure the dev struct is not global
PiOS LSM303: Move the configured flag into the device structure.  Make sure the
task doesn't try and run before the device is valid.
PIOS L3GD20: Swap the axis to the standard orientation on the FlyingF3.  This
will need to be confiugrable if someone else uses the L3GD20.
Sensors: To avoid warnins and errors for FlyingF3 allow up to 1 ms
to wait for accel data.  This is because the gyro and accel are not
synchronous on this board.
INSGPS: Add accessor method to get at the internal Nav structure
Makesfiles: Enable  -Wl,--warn-common and  -Wl,--fatal-warnings in all
the makefiles