Memory Leak Fix in Muxer.

- Track language_ and name_ member variables were not properly
  deleted.
- http://code.google.com/p/webm/issues/detail?id=416

Change-Id: Id0da669c347270cd355ad0b5e1e45ebf6415e367

mkvmuxer.cpp

@@ -395,6 +395,8 @@ Track::Track()
 Track::~Track() {
   delete [] codec_id_;
   delete [] codec_private_;
+  delete [] language_;
+  delete [] name_;
 
   if (content_encoding_entries_) {
     for (uint32 i = 0; i < content_encoding_entries_size_; ++i) {