app-misc/tmux-1.5 failed to compile with undefined symbols _res_9_b64_ntop. It needs -lresolv option on OS X. I will attach a patch to check this symbol in configure (against configure.ac), though I don't know whether it causes a bad effect on other platforms or it's safe.
Created attachment 280695 [details, diff] against configure.ac It checks res_9_b64_ntop in resolv.
Created attachment 280697 [details] tmux-1.5.ebuild added src_prepare to do patch and autoreconf.
(In reply to comment #1) Please rename the patch tmux-1.5-resolv.patch when to use with attached ebuild.
confirmed, patch works
I forgot to mention. I reported this to the upstream in http://sourceforge.net/tracker/?func=detail&aid=3376684&group_id=200378&atid=973262 but they closed it without applying my patch, because they "have a fix waiting for testing". So, please consider my patch is just a temporary one for 1.5 only, until the next release will come with a clean fix.
committed + fixes for Prefix