Windows splitting: prefer only 2 windows horizontal spliting.

[Oleksandr Gavenko (aka gavenkoa)]

How prefer horizontal splitting I know:

(when window-system
  ;; Prefer horizontal windows splitting.
  (setq split-height-threshold 0)
  (setq split-width-threshold nil)
  )

But how stop Emacs from splitting when already 2 windows?
So reuse existing window.

For example I edit file (1 window) then M-x compile (2 windows)
then C-x ` (2 windows, *Compilation* and source with error) -
no other window appear.

Emacs 23.1/22.3/21.4 work in such way on Debian, but new Emacs 23.2.1
work different.

For example: open file, C-x v l (new window show log),
d (new window show diff, there are 3 windows now),
M-x man printf RET (new window show man, there 4 windows now).

So how force Emacs display no more that 2 windows at same time?