potential version 2.18 is looking good

[Keith OHara]

A different score is at <http://k-ohara.oco.net/Lilypond/> chosen to show off 
the improvements made since version 2.16 (even the skyline-spacing of text that I 
tried to throw out) and with source that complies both with version 2.16 and current 
(which took some effort).

There are workarounds in the source, but only for known bugs in both versions.

Maybe we want to give naturals on sixths just a bit of separation, but there is 
an easy plan for that noted at the end of tracker issue 2141

There are some accidentals getting too close to rests (which can be resolved 
with pitched rests). I noted on the tracker that issue 472 has come back in 
some cases.