vdata_id	IN:	Vdata identifier returned by VSattach
	field_index	IN:	Index of the field

	Purpose	Returns the number of attributes attached to a vdata or the number of attributes attached to a vdata field.
	Return value	Returns the number of attributes assigned to this vdata or its fields when successful, and FAIL (or -1) otherwise.
	Description	VSfnattrs returns the number of attributes attached to a vdata specified by the parameter vdata_id, or the number of attributes attached to a vdata field, specified by the field index, field_index.
		To return the number of attributes attached to the vdata , set the value of field_index to _HDF_VDATA (or -1). To return the number of attributes of a field in the vdata , set the value of field_index to the field index. Field index is a nonnegative integer less than the total number of the vdata fields. The number of vdata fields is returned by VFnfields.
		VSfnattrs is different from the VSnattrs routine, which returns the number of attributes of the specified vdata and the fields contained in it.

	FORTRAN	integer function vsffnas(vdata_id, field_index)
		integer vdata_id, field_index