BLNDVX ( vertex, radius, neweds, newvxs, ifail )
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  Blends vertices on sheets and wires.

Receives:
  KI_tag_list_vertex       *vertex         --- vertex or vertices to blend
  KI_dbl_distance          *radius         --- blend radius

Returns:
  KI_tag_list_edge         *neweds         --- list of new edges
  KI_tag_list_vertex       *newvxs         --- list of new vertices
  KI_cod_error             *ifail          --- failure code

Specific errors:
  KI_wrong_surface          surfaces not suitable
  KI_invalid_bodies         invalid body
  KI_edges_intersect        blends would intersect
  KI_blends_overlap         blends would overlap
  KI_cant_blend_vertex      blending can't be done
  KI_wrong_number_edges     not two edges at vertex
  KI_solid_body             vertices on solid body
  KI_different_bodies       vertices on different bodies
  KI_general_body           general body

Description:
  Blends vertices from sheet or wire bodies with the given radius.

  Only two edges should meet at the vertex, and these two edges must share a
  common plane.  If the face between the two edges has a surface then it must
  be planar. A circular blend is created between the two edges.

  All vertices in the list should belong to the same body.

  If the two edges at the vertex are parallel so that the profile of the body
  is smooth across the vertex then that vertex will be ignored.
  If blending is not possible for any one of the vertices in the list for any
  other reason then none of the blending will be done.

  If the body is planar then a valid body will be returned. If the body is
  non-planar then blending may create a self-intersecting body. In this case if
  local checking is on then the function will return an ifail stating that the
  body is invalid.

  If any loop on a face is excluded from the face by a blend then this loop
  will be removed from the body.

  Lists of the blend edges and the new vertices are returned.

  This function is not supported for vertices on general bodies.