bug#10348: 24.0.92; Save and load window states

[Juri Linkov]

> Unless you have a better suggestion I'll apply (1) for Emacs 24.1 and
> try to propose a combination of (3) and (4) for later releases.

(7) Save window ids as numbers for referencing them when reading, e.g.

  (...
   (hc
    ...
    (id 3)
    (parameters
     (clone-of . 7))
    (leaf
     ...
     (id 7)
     (parameters
      (clone-of . 9))
     (buffer "*scratch*" ...))
    (vc
     (id 9)
     (parameters
      (clone-of . 3))
      ...
      )))