Repositing Cues before Clusters

A whole new approach to repositioning Cues before Clusters. This
patchset adds a new function CopyAndMoveCuesBeforeClusters to the
Segment class. This function should be called after
Segment::Finalize() to obtain a copy of the same output file with
Cues positioned before the Clusters.

Removing everything else that was added to accomplish the same in
the previous few commits.

Also, adding std:: qualifier to one of the variables in
sample_muxer_metadata which was missed accidentally in the previous
commit.

Change-Id: I2810d06a6251325add2f5e54d32d1da6e2fe143f

sample_muxer_metadata.cc

@@ -168,7 +168,7 @@ bool SampleMuxerMetadata::AddChapter(const cue_t& cue) {
   iter_t i = cue.payload.begin();
   const iter_t j = cue.payload.end();
 
-  string title;
+  std::string title;
 
   for (;;) {
     title += *i++;