CRSIPS ( bc, point, direct, angle, bs, ifail )
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  Swing a B-curve into a B-surface

Receives:
  KI_tag_b_curve           *bc             --- B-curve to swing
  KI_vec_position           point          --- point on axis of rotation
  KI_vec_axis               direct         --- direction of axis of rotation
  KI_dbl_angle             *angle          --- angle of swing (in radians)

Returns:
  KI_tag_b_surface         *bs             --- result of swing
  KI_cod_error             *ifail          --- failure code

Specific errors:
  KI_bad_angle              'angle' must not be zero
                            'angle' must be between -2pi and 2pi

Description:
  The B-curve is moved along an arc specified by the axis leaving a B-surface
  in its wake.

  'angle' must not be greater than 2pi or less than -2pi.
  'angle' must not be zero.

  Returned surface 'bs':
  . The curve lies along the v = 0 parameter line of the surface.
  . The surface is rational.
  . The u order of the surface is the order of the curve.
  . The v order of the surface is 4.
  . The surface will be periodic in u if  the curve is periodic.
  . The surface will be periodic in v if  'angle' is 2pi or -2pi.
  . For positive angles the curve will be spun anticlockwise when viewed down
    the axis ( ie. the right hand screw rule applied to the axis gives the spin
    direction ) and the surface normal will be in the direction of the cross
    product of the curve tangent and the spin direction.

  In general this procedure may construct a self-intersecting surface.