bug#3413: 23.0.94; ispell choices buffer display problem

1. emacs -Q
2. Type `thre threee'
3. Type `C-x 2' twice.  Now the frame has three windows stacked
   vertically, in the lowest window (window-height) returns 18, in each
   of the two upper windows (window-height) returns 9.
4. Make either of the two upper windows the selected window, and in that
   window make the text typed in step 2 an "active region" (select with
   the mouse or type `C-a C-SPC C-e').
5. Type `M-$' 
=> The selected window splits vertically, in the lower one of these,
   `thre' is highlighted, the upper window contains a two-line high
   *Choices* buffer displaying 10 corrections for `thre'.
6. Type `SPC'
=> In the lower window now `threee' is highlighted, the *Choices*
   buffer in the upper window displays one empty line, and is
   unscrollable.
   
If at step 4 the window with (window-height) 18 is selected, then step 5
is the same, but in step 6, the *Choices* buffer is five lines high and
shows 28 alternatives for `threee'.

In GNU Emacs 23.0.94.1 (i686-pc-linux-gnu, GTK+ Version 2.14.4)
 of 2009-05-28 on escher
Windowing system distributor `The X.Org Foundation', version 11.0.10502000
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=local
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t