* usr/share/byobu/profiles/bashrc:
  - adjust whitespace
* usr/bin/byobu:
  - handle the backend better
* etc/byobu/backend, usr/lib/byobu/include/common:
  - really default to tmux, at this point
  - tmux was the default in the previous LTS
* usr/lib/byobu/include/common:
  - simplify backend detection
releasing 5.64
opening 5.65