[O] Bug: `org-edit-special` doesn't respect dedicated windows

[Alexis]

Context:

Manually compiled Emacs 24.4.1 on Debian Wheezy(+updates) x86_64.

ECM:

1. emacs -Q
2. Split frame into two windows via `C-x 3`.
3. Make one "*scratch*" buffer window dedicated via:
  (a) `M-:`
  (b) (set-window-dedicated-p (selected-window) t)
4. Select the other window.
5. Visit file `test.org`, containing:

   * Test
   #+begin_src emacs-lisp
     (message "Test.")
   #+end_src

6. Move point within source block, do `org-edit-special`.
7. The "*scratch*" buffer window will have its contents changed to 
  contain an Org buffer.


Alexis.