bug#10348: 24.0.92; Save and load window states

[martin rudalics]

> (7) Save window ids as numbers for referencing them when reading, e.g.
>
>   (...
>    (hc
>     ...
>     (id 3)
>     (parameters
>      (clone-of . 7))

I did something like that in revision #104759.  Note, however, that
numbers work reliably only when using `window-state-put' in one and the
same session as the corresponding `window-state-get'.  It would be
rather difficult to make them work across sessions.

martin