[AD] Fix window switch problem on exit (Windows)

[Eric Botcazou <ebotcazou@xxxxxxxxxx>]

The attached patch aims at fixing the problems reported for Allegro programs 
on exit, mainly under WinXP (I don't see them on Win98SE): the programs 
don't completely shut down, because one of the threads is blocked.

This happens because the initial switch mode (SWITCH_PAUSE) is reset on exit 
by the Windows port. So if the window happens to loose the focus during the 
exit phase, and a timer is still running, the timer thread waits for the 
window to regain the focus, which never happens. It seems that the window is 
very likely to loose the focus on destruction under WinXP, contrary to 
Win98SE for example.

Applied to mainline and branch.

-- 
Eric Botcazou

Attachment: win_switch_mode.tar.gz
Description: application/tgz