change of COORDINATES (2)	Jun/17 Matsui

:copy-coords and :inverse-transformation methods have been extended
to accept optional result argument. If no argument is given to these
methods, a new instance of coordinates which has the identical value
with self, or which has the inverse-transformation to self, is created.
If another instance of coordinates is given, the resulted copy or inverse
is stored there.

(setq a (make-coords :pos #f(10 20 30) :rpy '(0.1 0.2 0.3)))
(setq b (make-coords))
(send a :copy-coords b)
(eq a b)  --> NIL (different objects, of course)
(equal a b)  --> T (but contents are identical)

; (send a :copy-coords b) has the same effect as (send b :replace-coords a)

(send a :inverse-transformation b)
(equal (send a :inverse-transformation) b)  --> T
