all-font-metrics, span bars

[Juergen Reuter]

Actually, I am currently on vacation and can not really work on lily, but
I accidentally noticed that 1.7.30 breaks the ancient font, so I put a
tiny fix in cvs.

I also noticed that input/test/bar-lines-lyric-only.ly is still (or once
again?) broken:

* Bars should be removed from the staff:

    \translator {
      \StaffContext
      \remove "Bar_engraver"
    }

* The span bar spans only across the lyrics context but not the remaining
  inter-staff place (e.g. where the notes on ledger lines are).

* Main application for this notation style is probably mensural vocal
  music, hence you may want to choose ChoirStaff rather than StaffGroup
  for the example.

Greetings,
Juergen