Beaming problem introduced with 2.13.60

[Nick Payne]

Example below demonstrates (a couple of bars taken from Bach's 
chaconne). This problem did not exist in versions prior to 2.13.60:

%=============================
\version "2.13.60"
\language "english"

\relative c' {
    \time 3/4
    \key d \minor
    \stemUp
    d,16 bf''' bf gs gs f f d d b gs e |
    \stemDown cs a'' a fs fs ef ef c \stemUp c a fs( d) |
}
%=============================

The console log contains

Drawing systems...
programming error: No viable beam quanting found.  Using unquanted y value.
continuing, cross fingers
/home/nick/lilypond/examples/test.ly:9:18: warning: weird stem size, 
check for narrow beams
    \stemDown
                  cs a'' a fs fs ef ef c \stemUp c a fs( d) |
programming error: No viable beam quanting found.  Using unquanted y value.
continuing, cross fingers
/home/nick/lilypond/examples/test.ly:9:39: warning: weird stem size, 
check for narrow beams
    \stemDown cs a'' a fs fs ef ef
                                       c \stemUp c a fs( d) |

And the output looks like

test.preview.png
Description: PNG image