Alterations above an articulation

[Maurizio Tomasi]

If I compile the following code with Lilypond 1.5.x (currently I am
using version 1.5.63, but this happened with older versions too):

----------------------------------------------------------------------
smallNatural = #'(music ((font-relative-size . -1) "accidentals-0"))

\score {
    \context Staff \notes \relative c'' {
        \key f \minor

        c2^\prall^\smallNatural c2^\trill^\smallNatural
    }
}
----------------------------------------------------------------------

then the first natural sign goes *above* the prall (as one would
expect), but the second one goes *below* the trill. Is this a bug, or
does Lily *have to do* this for some strange typesetting convention?

Another question. We already discussed about a similar topic in this
mailing list (20/06/2002): the problem was to place two alterations
near a turn, the first above the articulation while the other below it
(but *above* the note), since Lily swaps the lower alteration with the
articulation. It seems to me that Han-Wen did found the reason of this
strange behaviour (it was something about `script-priority'), so I
thought this was a bug to be corrected. But Lily 1.5.63 still gives
the same output as the previous versions.

Maurizio