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

	Purpose	Deletes an object from a vgroup.
	Return value	Returns SUCCEED (or 0) if successful and FAIL (or -1) if not successful or the given tag/reference number pair is not found in the vgroup.
	Description	Vdeletetagref deletes the object specified by the parameters tag and ref from the vgroup identified by the parameter vgroup_id. Vinqtagref should be used to check if the tag/reference number pair exists before calling this routine.
		If duplicate tag/reference number pairs are found in the vgroup, Vdeletetagref deletes the first occurrence. Vinqtagref should be used to determine if duplicate tag/reference number pairs exist in the vgroup.

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