improve zsh, automatically ... (pulled from configure)

  if test -n "${ZSH_VERSION+set}" && (emulate sh) >/dev/null 2>&1; then
    emulate sh
    NULLCMD=:
    # Zsh 3.x and 4.x performs word splitting on ${1+"$@"}, which
    # is contrary to our usage.  Disable this feature.
    alias -g '${1+"$@"}'='"$@"'
    setopt NO_GLOB_SUBST
  else