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   Rotate a geometric state to the circular phase angle phi.
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   Form:
   g = RotateState( g, phi );
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   Inputs
   ------
   g            (.)    Geoemtric goals data structure (see Geometry_Structure)
   phi          (1)    Circular phase angle (see CirclePhase)

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   Outputs
   -------
   g            (.)    New geoemtric goals data structure, rotated to phi

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