bug#5740: 24.0.50; Gomoku display bug

[Stephen Berman <stephen.berman@gmx.net>]

1. emacs -Q
2. M-x gomoku
3. Play until the game is won, then press RET, which clears the board.
=> The positions occupied at the end of the just cleared board display a
residue of the characters -- a thin red line from the right side of the
`O' and two green dots from the right side of the `X'.  Typing C-l
eliminates the residue.

This is with the default font on my system:
xft:-monotype-Andale Mono-normal-normal-normal-*-12-*-*-*-m-0-iso10646-1
Normally I use this font:
xft:-unknown-DejaVu Sans Mono-bold-normal-normal-*-12-*-*-*-m-0-iso10646-1
and with this the above bleeding does not occur (with the Andale Mono
font I can see that the Gomoku `O' and `X' characters are slightly wider
than the block cursor, while with DejaVu Sans Mono they are just as wide
as the cursor).

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