I modified the ncurses makefile.

I discovered after deploying tmux 1.9a that it fails with this error:

    open terminal failed: missing or unsuitable terminal: xterm-256color

This page contains fixes:

    http://pyther.net/2014/03/building-tmux-1-9a-statically/

I modified make/ncurses.mk to pass the --with-default-terminfo-dir and
--with-terminfo-dirs options to "configure".