bug#5739: 24.0.50; Gomoku mouse placement bug

[Stephen Berman]

1. Let ~/.emacs consist of this sexp, for example (anything that makes a
default header line -- crucially in the init file -- will do):
(setq-default header-line-format "test")
2. Start Emacs with the above init file.
3. M-x gomoku
4. When the human player uses the mouse to make moves and positions the
mouse pointer such that it is as low as possible within the chosen
position -- i.e., the position is highlighted but the dot is visible --
then the completed move occupies the the position immediately below the
one aimed at (or if the lower position is occupied, Gomoku will
complain, even though the mouse pointer is clearly on a free position,
as evidenced by the highlighting).

In GNU Emacs 24.0.50.1 (i686-pc-linux-gnu, GTK+ Version 2.18.6)
 of 2010-03-19 on escher
Windowing system distributor `The X.Org Foundation', version 11.0.10605000
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