ENVETY ( vertex, vetype, ifail )
================================

  Enquire vertex type

Receives:
  KI_tag_vertex            *vertex         ---  vertex

Returns:
  KI_cod_enve              *vetype         --- type-code of vertex,
                                           --- from range ENVE00
  KI_cod_error             *ifail          --- failure indicator

Specific errors:
  KI_general_body           general body

Description:
  The type of vertex is returned as one of the following codes:

      ENVEIS  ---  isolated vertex (no edges)
      ENVESP  ---  spur vertex (single edge, one end only)
      ENVEWR  ---  wire vertex (all edges are wires)
      ENVENO  ---  normal vertex

  For a definition of 'wires' see ENEDTY.

  This is not supported for vertices on general bodies.