Now that all my hosts are running new enough userlands to support the tmux-256color terminfo entry I can use it everywhere. Notably this enables italics to work inside tmux. Also update comment about the tmux-specific terminfo extensions for true color. I need to keep using "Tc" until all my hosts have tmux 3.2+. See: https://jdhao.github.io/2018/10/19/tmux_nvim_true_color/ See: https://github.com/tmux/tmux/wiki/FAQ#i-dont-see-italics-or-italics-and-reverse-are-the-wrong-way-round