Hang caused by Dynamic_align_engraver

[Dan Eble]

> I'm not top posting.
\version "2.18.0"
\layout {
  \context {
    \Voice
    % Adding this engraver makes Lilypond take a really long time to
    % run--possibly until the end of time.  Even if it doesn't make
    % sense, the failure mode could be improved.
    \consists "Dynamic_align_engraver"
  }
}
\relative f'' { f-\f }