Re: Fix for beaming in Kievan notation (issue 6305080)

[aleksandr . andreev]

This is definitely not an elegant approach to the problem at all (and it
does not solve the issue of the warning being given out at stem.cc line
128), but it's the best I can figure out after hacking at the code for a
while.

Perhaps reviewers more familiar with LilyPond internals can provide some
comments for improvement.

http://codereview.appspot.com/6305080/