port info: Re-implement broken subfield separators
port info: Re-implement broken subfield separators

The subfield_sep variable was not used anymore after 30c27d5, replace it
with specific separators for the different output modes.

Closes: https://trac.macports.org/ticket/52928

macports/macports-base,neverpanic/macports-base,danchr/macports-base,danchr/macports-base,neverpanic/macports-base,macports/macports-base