vgroup_id	IN:	Vgroup identifier returned by Vattach
	tag	IN:	Tag of the object
	ref	IN:	Reference number of the object

	Purpose	Inserts an object into a vgroup.
	Return value	Returns the number of objects in the vgroup if successful and FAIL (or -1) otherwise.
	Description	Vaddtagref inserts the object identified by the parameters tag and ref into the vgroup identified by the parameter vgroup_id.
		If an object to be inserted is a data set, duplication of the tag/reference number pair will be allowed. Otherwise, the tag/reference number pair must be unique among the elements within the vgroup or the routine will return FAIL (or -1).

	FORTRAN	integer function vfadtr(vgroup_id, tag, ref)
		integer vgroup_id, tag, ref