CRSPSU ( centre, radius, sphere, ifail )
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  Create a spherical surface.

Receives:
  KI_vec_centre             centre         --- centre position
  KI_dbl_radius            *radius         --- radius of sphere

Returns:
  KI_tag_surface           *sphere         --- new spherical surface
  KI_cod_error             *ifail          --- failure code

Specific errors:
  KI_radius_too_large       radius too large

Description:
  A new spherical surface is created with centre 'centre' and radius
  'radius'. The surface normal points away from the centre position.