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   Generic aircraft sensor. Outputs are
   z acceleration
   roll rate       (rad/sec)
   angle of attack (deg)
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   Form:
   g = ACSensor( x, d, opt )
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   Inputs
   ------
   x           (:)   acstate data structure
   d           (:)   Aircraft data structure
   opt               'rhs'  outputs state derivatives
                     'meas' outputs measurements

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   Outputs
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   g           (:)   Sensor output
                     .aN        (1,1) Normal acceleration
                     .q         (1,1) Pitch rate
                     .alpha     (1,1) Angle of attack
                     .p         (1,1) Roll rates
                     .r         (1,1) Yaw rates
                     .altitude  (1,1) Altitude
                     .machNo    (1,1) Mach number
                     .qBar      (1,1) Dynamic pressure

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