Clarify with-ode-integration used for scalar dependent variables

;; ODE system setup

;; Liam Healy, Sun Apr 15 2007 - 14:19

;; Time-stamp: <2010-06-30 19:57:28EDT ode-system.lisp>

;; Time-stamp: <2011-05-04 10:25:19EDT ode-system.lisp>

;;

;; Copyright 2007, 2008, 2009 Liam M. Healy

;; Copyright 2007, 2008, 2009, 2010, 2011 Liam M. Healy

;; Distributed under the terms of the GNU General Public License

;;

;; This program is free software: you can redistribute it and/or modify

	       &key jacobian (scalarsp t) (stepper '+step-rk8pd+)

	       (absolute-error 1.0d-6) (relative-error 0.0d0))

     &body body)

  "Environment for integration of ordinary differential equations."

  ;; Note: the case jacobian=nil is not properly handled yet; it

  ;; should put a null pointer into the struct that is passed to GSL.

  "Environment for integration of ordinary differential equations when dependent variables are individually named scalars."

  ;; Note: If the dependent variables are in a foreign array, it is

  ;; best to call the ODE functions directly; this macro is just

  ;; provided as a convenience if they are separate scalars.

  ;; Note:

  ;; the case jacobian=nil is not properly handled yet; it should put

  ;; a null pointer into the struct that is passed to GSL.

  (let ((dep (make-symbol "DEP"))

	(ctime (make-symbol "CTIME"))

	(cstep (make-symbol "CSTEP")))