Ambitus incorrect upper note

[Trevor Daniels]

A bug in the ambitus engraver seems to have crept in between
2.11.34 and 2.11.36.  The example in section 3.3.5 of the
Learning Manual at
http://kainhofer.com/~lilypond/Documentation/user/lilypond-l
earning/Adding-and-removing-engravers.html#Adding-and-removi
ng-engravers which was compiled with 2.1.36 is incorrect -
the top note should be a C, not a B.  The same example
compiled in 2.11.34 is correct.  Here's a minimal example:

\new Staff <<
  \new Voice \with {
    \consists Ambitus_engraver
  }
  \relative c'' {
    \voiceOne
    c a b g
  }
>>

Trevor D