bug#7464: 24.0.50; mouse highlighting vanishes upon unsplitting window

[Stephen Berman]

1. emacs -q
2. C-x 2
3. Put the mouse pointer over one of the links in the splash screen, so
that the link becomes highlighted.
4. C-x 1
=> The highlighting from step 3 disappears, although the mouse pointer
is still over the link.  If the cursor is moved onto the link, then the
character under the cursor shows highlighting again, and moving the
cursor within the link extends the highlighting.

This problem is reliably reproducible, also on earlier builds of Emacs
24 I have, but not on Emacs 23.1.91 (I don't have 23.2).

In GNU Emacs 24.0.50.1 (i686-pc-linux-gnu, GTK+ Version 2.18.6)
 of 2010-11-22 on escher
Windowing system distributor `The X.Org Foundation', version 11.0.10605000
configured using `configure  '--without-toolkit-scroll-bars''

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