Transmission-2.13 requires only a small patch to make it compatible with libnotify-0.7
Created attachment 260259 [details, diff] transmission-libnotify-0.7.patch
+ 29 Jan 2011; Samuli Suominen <ssuominen@gentoo.org> transmission-2.13.ebuild, + +files/transmission-2.13-libnotify-0.7.patch: + Fix building with x11-libs/libnotify >= 0.7 wrt #352128 by Priit Laes.