CRCICU ( centre, axis, radius, circle, ifail )
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  Creates a circular curve.

Receives:
  KI_vec_centre             centre         --- centre of circle
  KI_vec_axis               axis           --- axis direction
  KI_dbl_radius            *radius         --- radius of circle

Returns:
  KI_tag_curve             *circle         --- circular curve
  KI_cod_error             *ifail          --- failure code

Specific errors:
  KI_radius_too_large       radius is too large

Description:
  A complete circle is created with the given centre, radius, and axis
  direction. The sense of the circle is clockwise when looking along the
  axis direction.