For older systems use tmux-old-ncurses.bash (also added in this commit)
for forcing screen-256color instead.
From what I have understood the difference is that screen-256color
doesn't handle italics or something.
This reverts commit 74d57e0b0f.
* * * * *
Apparently my tests were flawed as seen after reboot and there is no
terminfo for tmux-256color even in Arch stable repos yet.