I hope I'm not making a mistake here, but I would have thought xorg-server should install /etc/init.d/xprint and other supporting files. This is because xorg-server is the successor of monolithic xorg-x11 for servers; xorg-x11-6.8.x installs /etc/init.d/xprint etc. when USE=xprint. I attach an ebuild patch which installs /etc/init.d/xprint, /usr/lib/misc/xprint, /etc/X11/xinit/xinitrc.d/92xprint-xpserverlist.sh, /etc/profile.d/xprint.{sh,csh}. The ebuild patch is based on the USE=xprint code in xorg-x11-6.8.2-r6.ebuild; it also uses xprint.init from xorg-x11 files.
Created attachment 83008 [details, diff] xorg-server-1.0.2-r1-xprint.diff
Created attachment 83009 [details] xprint.init
Ebuild is in my overlay at http://catmur.co.uk/svn/repos/gentoo/tree
Fixed, thanks!