use gcc attributes to align and pack

msg/templates/uorb/msg.h.template

src/drivers/device/integrator.cpp

src/drivers/device/integrator.h

src/drivers/l3gd20/l3gd20.cpp

src/drivers/lsm303d/lsm303d.cpp

src/drivers/mpu6000/mpu6000.cpp

src/drivers/mpu6500/mpu6500.cpp

src/drivers/mpu9250/mpu9250.cpp

src/drivers/px4flow/px4flow.cpp

src/lib/conversion/rotation.cpp

src/lib/conversion/rotation.h

src/modules/mavlink/mavlink_receiver.cpp

src/modules/uORB/uORB.h

src/platforms/posix/drivers/gyrosim/gyrosim.cpp