an_id	IN:	AN interface identifier returned by ANstart
	obj_tag	IN:	Tag of the object to be annotated
	obj_ref	IN:	Reference number of the object to be annotated
	annot_type	IN:	Type of the data annotation

	Purpose	Creates a data annotation for an object.
	Return value	Returns the data annotation identifier (ann_id) if successful and FAIL (or -1) otherwise.
	Description	ANcreate creates a data annotation of type annot_type for the object specified by its tag, obj_tag, and its reference number, obj_ref. The returned data annotation identifier can represent either a data label or a data description.
		Valid values for annot_type are AN_DATA_LABEL (or 0) or AN_DATA_DESC (or 1).
		Use ANcreatef to create a file annotation.
		Currently, the user must write to a newly-created annotation before creating another annotation of the same type. Creating two consecutive annotations of the same type causes the second call to ANcreate to return FAIL (or -1).

	FORTRAN	integer function afcreate(an_id, obj_tag, obj_ref, annot_type)
		integer an_id, obj_tag, obj_ref, annot_type