extender line bug

[Erik Sandberg]

Here are 2 new examples of bugs in the extender:

\version "2.1.17"
\score {
 << % the extender is not output at all
  \context Voice=A \notes {  \times 2/3 {a8( a a a a a} a4) r | a16 }
  \lyricsto A \context LyricsVoice \lyrics { a __ a }
 >>
}

\score {
 << % the extender is too long
  \context Voice=A \notes {  \times 2/3 {a8( a a a a a} a4) r \break | a16 }
  \lyricsto A \context LyricsVoice \lyrics { a __ a }
 >>
}