Re: Gets rid of length in the docs. (issue 4965053)

[percival . music . ca]

amusingly, I have no trouble compiling the docs without this patch, but
it fails with this patch applied:

/main/src/lilypond/build/out/lybook-db/b5/lily-2dcca534.ly:1097:9:
warning: no viable initial configuration found: may not find good beam
slope
        <
         c ees>8 f g
Segmentation fault


I think that came from the essay, in case you want to just compile that
specific manual to test.  (instructions recently added to the CG)

http://codereview.appspot.com/4965053/