* /etc/zsh/zshrc:

    - move power completion / abbreviation expansion from /etc/skel/.zshrc to
      main zsh config file so we can use it as root as well (thanks for hint,
      wuehlmaus)
    - support setting of RPROMPT via $DONTSETRPROMPT (thanks ft!)
    - allow setting NOPRECMD=1 without starting new zsh (thanks, ft!)
  * /etc/skel/.zshrc: rework function dirspace() [support $1]