[PATCH] Porrectus: first try

[Juergen Reuter]

Hi!

Attached is a patch that introduces porrectus support for lily.  There are
still a lot of issues left (see comments in porrectus-engraver.cc), but
basically, it should work.

Immediately before packaging this patch, I just discovered something
strange that might be a bug in lily's line breaking algorithm, but this
needs more investigation to be sure: setting a note head's transparent
property to ##t seems to make invisible the head's stem and accidentals
only in the first line of score.  I guess this is not intended behaviour,
right?

Greetings,
           Juergen

patch.txt
Description: patch