* lily/voice-devnull-engraver.cc (acknowledge_grob): Use proper

* lily/voice-devnull-engraver.cc (acknowledge_grob): Use proper
spelling for always.  In solo a due mode, kill spanners when the
other thread has solo.

* lily/thread-devnull-engraver.cc (acknowledge_grob): In solo a
due mode, kill everything when the other thread has solo.

* lily/a2-engraver.cc (acknowledge_grob): In solo a due mode, do
not set directions when we have solo.

* lily/part-combine-music-iterator.cc (process): Set property
"othersolo" if the other thread has solo.