vdata_id	IN:	Vdata access identifier returned by VSattach
	field_name_list	OUT:	List of field names

	Purpose	Retrieves the names of the fields in a vdata.
	Return value	Returns SUCCEED (or 0) if successful and FAIL (or -1) otherwise.
	Description	VSQueryfields retrieves the names of the fields in the vdata identified by the parameter vdata_id into the parameter field_name_list.
		The parameter field_name_list is a comma-separated list of the fields in the vdata. (i.e., "PX,PY,PZ" in C and 'PX,PY,PZ' in Fortran).

	FORTRAN	integer function vsqfflds(vdata_id, field_name_list)
		integer vdata_id
		character*(*) field_name_list