* usr/bin/byobu-launch:
  - append, rather than prepend, $PROMPT_COMMAND, as double-semi-colons
    are illegal, thanks to Christian Mäder in github for patch
* usr/bin/byobu, usr/lib/byobu/include/Makefile.am,
  usr/lib/byobu/include/tmux-detach-all-but-current-client,
  usr/share/byobu/keybindings/f-keys.tmux,
  usr/share/byobu/keybindings/f-keys.tmux.disable,
  usr/share/doc/byobu/help.tmux.txt: LP: #939870
  - add a new keybinding, Alt-F6, which detaches all other clients
    + often used to maximize your tmux session, since tmux reduces
      the available size of your terminal to the smallest connected
      session