OUSPCU ( spc, surf, ctrl, dim, order, nctrl, knots, period, ifail )
===================================================================

  Output an SP-curve in B-spline form.

Receives:
  KI_tag_curve             *spc            --- SP-curve

Returns:
  KI_tag_surface           *surf           --- basis surface of SP-curve
  KI_tag_list_dbl          *ctrl           --- control points
  int                      *dim            --- vertex dimension (2 or 3)
  KI_int_order             *order          --- order of curve
  KI_int_nitems            *nctrl          --- number of control points
  KI_tag_list_dbl          *knots          --- knot values
  KI_cod_logical           *period         --- periodic flag
  KI_cod_error             *ifail          --- failure indicator

Specific errors:
  KI_bad_type               non-sp curve supplied

Description:
  OUSPCU will, given the tag of an SP-curve, output the SP-curve's data.

  An SP-curve describes a 3-space curve in (2-dimensional) parameter space
  of a surface.

  The SP-curve consists of general B-spline curves in surface parameter
  space (i.e. curves with (u,v) instead of (x,y,z) vertices, where u & v
  are the parameters of the surface). SP-curves can be rational, in which
  case 'dim' is 3, and the vertices are (u,v,w) vectors.

  The SP-curve parameterisation is governed by the range of the knot
  vector 'knots'.

  The following data is output:

  (1) The surface ('surf') in whose parameter space the SP-curve has been
      computed.

  (2) The B-spline control points 'ctrl'.

  (3) The vertex dimension 'dim', which will be 2 for non-rational curves,
      and 3 for rational ones.

  (4) The order of the SP-curve 'order'.

  (5) The number of control points 'nctrl'.

  (6) The knot vector 'knots'. There will be 'nctrl' + 'order' of these.

  (7) If the B-spline is periodic, 'period' is set to KI_true.

  Periodics:

  Parasolid may choose to treat an SP-curve as periodic if it is closed and
  G1 continuous even if the B-spline is not periodic and 'period' is KI_false,
  ENCUPA reflects this internal periodicity.