All x11-wm/icewm ebuilds specify wrong dependencies for xinerama support. Currently, there is a forced dependency for x11-proto/xineramaproto, which is not needed if xinerama is not wanted. AFAICT, it should be the following way: RDEPEND="... xinerama? ( x11-libs/libXinerama )..." DEPEND="${RDEPEND} ... xinerama? ( x11-proto/xineramaproto )..."
Fixed in CVS, thanks