[kde-sunset] xorg-server-1.7.5.901 breaks Alt+Tab from rxvt-unicode

Hi there!

As I just reported in https://bugs.gentoo.org/show_bug.cgi?id=308795 the
recent update of xorg-server breaks Alt+Tab for rxvt-unicode: when I've
got a urxvt window focused, pressing Alt+Tab won't switch app.

As the issue seems to be specific to KDE 3.5, I guess we'll have to
address it in kde-sunset if at all. Is there someone around here who has
an idea how these different components might interact to cause this bug?
Why is it only urxvt, not every app? Why is it KDE 3.5 but not KDE 4.4?
Why did everything work in xorg-1.7.5 but breaks in 1.7.5.901?

I'd like to investigate this further, but I don't have the slightest
idea where to start, short of grepping sources for rxvt-unicode, xorg
and kwin for any references related to Alt+Tab app switching.

Greetings,
 Martin

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