Download Libevent and Tmux.

mkdir ~/build
cd ~/build
curl -OL http://downloads.sourceforge.net/tmux/tmux-1.9a.tar.gz
curl -OL http://downloads.sourceforge.net/project/levent/libevent/libevent-2.0/libevent-2.0.16-stable.tar.gz

Extract.

tar zxvf libevent-2.0.16-stable.tar.gz
tar zxvf tmux-1.9a.tar.gz

Install.

// Libevent

cd libevent-2.0.16-stable/
./configure --prefix=/usr/local/libevent
make
sudo make install

// Tmux
cd tmux-1.9a
LDFLAGS="-L/usr/local/libevent/lib" CPPFLAGS="-I/usr/local/libevent/include" LIBS="-lresolv" ./configure --prefix=/usr/local/tmux
make
sudo make install