Dynamics over-lapping with bar-lines

[David Sumbler]

Following the problem I was having with dynamics in a flute part and a
piano part not lining up, on the advice of the list I upgraded my
LilyPond from v2.14.2 to 2.18.0.

Problem of non-alignment solved.

But I still find that dynamics often contact or even cross a bar-line.
In the flute part of this piece it does not matter, of course, because
the bar-line does not extend beyond the stave.  But in the piano part it
does matter.  The problem is the same whether the dynamic marks are
added in a Staff context or in a separate Dynamics context.

How do I tell LilyPond not to superimpose dynamics and bar-lines?

David