Feature request - contemporary trill indications

[Jamie Bullock]

Hi!

Is there any chance that someone could write a lilypond engraver for
contemporary trill notation? By this I mean the use of the usual trill
sign, with a small, stemless notehead in brackets after the main note,
indicating the 'auxilliary note' to be trilled with.

This notation technique is common in contemporary scores, such as those
by Boulez, and I use it a lot in my own work. To my knowledge there is
no other 'standard' method for indicating the auxilliary note of a trill
in atonal music. 

I have tried to work out a way of doing this with both lilypond 2.4.5
and 2.5.29, but I can't seem to find a method that works properly. Any
suggestions, even for a workaround would be much appreciated. 

-- 
Regards,

Jamie