Bug#348697: Explanation from upstream author

[Thomas Kappler <thomas.kappler@stud.uni-karlsruhe.de>]

I asked [1] Marc Lehmann about this issue, and he replied 

"rxvt-unicode neither installs nor comes nor requires a system-wide
app-defaults file, so it doesn't read one.

Administrators and users can create their own config by setting
XAPPLRESDIR."

I tested this on my system with 
    XAPPLRESDIR="/etc/X11/app-defaults"
and it works perfectly. So this should be documented in README.Debian or
the like.

Regards,
Thomas

[1] http://lists.schmorp.de/pipermail/rxvt-unicode/2006q1/000207.html