IDSCEN ( entity, contyp, conent, ifail )
========================================

  Identify single connected entity.

    Can be called from the GO.

Receives:
  KI_tag_entity            *entity         --- entity to look in
  KI_cod_ty                *contyp         --- type of desired entity

Returns:
 <KI_tag_entity>           *conent         --- entity found
  KI_cod_error             *ifail          --- failure indicator

Specific errors:
  KI_bad_type_combn         bad type combination
  KI_general_body           general body
  KI_not_a_tag              not an entity

Description:
  IDSCEN is similar to IDCOEN except it returns one entity or NULTAG in 'conent'
  rather than a list of entities.

  The valid combinations of the type of 'entity' and 'contyp' can be found by
  examining the table given for the function IDCOEN; only those combinations
  marked by 1 or 1* are valid for IDSCEN.

  This function is not supported for general bodies.

  If, in the type combination table given with IDCOEN, the cell for the type
  combination given is marked other than 1 or 1*, KI_bad_type_combn will be
  returned in 'ifail'.