Feature request: dashed bar lines

[Heikki Johannes Junes]

Contemporary music uses also bar lines which are dashed. Arvo Pärt, an
Estonian composer, for example, has written music, in which the length of a
bar can be very long and, instead, dashed bar lines structure the music.

Therefore, there should be a new type of bar lines, which is dashed.
It could be used with just `\bar "some symbol"'.

  Heikki