control of tie direction

[Werner LEMBERG]

As a follow-up to this bug report

  http://code.google.com/p/lilypond/issues/detail?id=139#c2

I wonder whether it is possible to control the direction of ties
within chords similar to that of slurs:

  \relative c' {
    <f^~ d'>(  <e f c'>)
  }

LilyPond accepts this but ignores the `^'.  This would be of great
help in handling complicated chords.


    Werner