Log Message:
tmux: Update misc/tmux to 2.8

pkgsrc changes:
 - Address -Wint-conversion warnings and properly cast to long, patch by
   <christos> from NetBSD, thanks!
 - Remove patch-server-client.c, timersub() was added in compat.h
   since tmux-1.9 and is no longer needed
 - Take MAINTAINERship

Changes:
2.8
---
 * Make display-panes block the client until a pane is chosen or it
   times out.
 * Clear history on RIS like most other terminals do.
 * Add an "Any" key to run a command if a key is pressed that is not
   bound in the current key table.
 * Expand formats in load-buffer and save-buffer.
 * Add a rectangle_toggle format.
 * Add set-hook -R to run a hook immediately.
 * Add README.ja.
 * Add pane focus hooks.
 * Allow any punctuation as separator for s/x/y not only /.
 * Improve resizing with the mouse (fix resizing the wrong pane in some
   layouts, and allow resizing multiple panes at the same time).
 * Allow , and } to be escaped in formats as #, and #}.
 * Add KRB5CCNAME to update-environment.
 * Change meaning of -c to display-message so the client is used if it
   matches the session given to -t.
 * Fixes to : form of SGR.
 * Add x and X to choose-tree to kill sessions, windows or panes.