#5315 Alternate repeats with different time signatures in a simultaneous music construct produces unexpected bar check errors

Reported by Arttu Punkkinen puukiuuki@gmail.com and Steven Weber panteck@hotmail.com

Arttu's example below

\version "2.19.65"
% Bar lines to do not reflect time signature change
<<
  {
    \repeat volta 2 {
    c'2 c'
    }
    \alternative {
      { c' c'}
      {\time 1/2 c' c'}
    }
  } \\
  {
    \repeat volta 2 {
      c' c'
    }
    \alternative {
      { c' c'}
      { c' c'}
    }
  }
>>

% Bar lines work correctly if change is in last context
<<
  {
    \repeat volta 2 {
      c' c'
    }
    \alternative {
      { c' c'}
      { c' c'}
    }
  } \\
  {
    \repeat volta 2 {
      c' c'
     }
    \alternative {
      { c' c'}
      {\time 1/2 c' c'}
    }
  }
>>

Works as expected in 2.18.2