Description of Problem: Current versions of kde in rahide come without support for xinerama. All current versions of X come with the necessary libraries and xinerama support is greatly enhanced with qt3. configuring kdelibs and kdebase with --with-xinerama just enables the xinerama controls in kde an not xinerama itself so it does no harm to people without xinerama. But it saves all the time of recompiling for xinerama users... Your qt3 already comes with configured-in xinerama support. So all you need to do is add --with-xinerama to the configure of kdelibs and kdebase.
Bero, a while back someone asked for this on IRC, and I chatted with you about it, and you mentioned it was disabled because it was broken, but that you hadn't tried it in a while. I took our 7.2 package, and rebuilt it for the guy with xinerama enabled for testing. He reported it works fine now. I havent tested it myself, however several others have found the rpm I put up and thanked me for it so I presume it is safe enough to enable now in KDE by default possibly. Officially we do not support xinerama of course, but if it is known to work, we might want to enable it just for the heck of it. I dont mind closing any XFree86 Xinerama bug reports with "sorry we dont support xinerama, we only provide it as a convenience due to popular request". ;o) Just thought I'd mention the success story.
kde 3 in 7.3 supports xinerama