mkvparser: read track language information

Track::GetLanguageAsUTF8 is implemented to allow the user to
choose between available audio and subtitle tracks.

Change-Id: I5ec9b1c1c00182da759681ba486cbace46e9b63f

mkvparser.cpp

@@ -5440,6 +5440,7 @@ long Track::Create(
 
 Track::Info::Info():
     nameAsUTF8(NULL),
+    language(NULL),
     codecId(NULL),
     codecNameAsUTF8(NULL),
     codecPrivate(NULL),
@@ -5457,6 +5458,9 @@ void Track::Info::Clear()
     delete[] nameAsUTF8;
     nameAsUTF8 = NULL;
 
+    delete[] language;
+    language = NULL;
+
     delete[] codecId;
     codecId = NULL;
 
@@ -5516,6 +5520,9 @@ int Track::Info::Copy(Info& dst) const
     if (int status = CopyStr(&Info::nameAsUTF8, dst))
         return status;
 
+    if (int status = CopyStr(&Info::language, dst))
+        return status;
+
     if (int status = CopyStr(&Info::codecId, dst))
         return status;
 
@@ -5570,6 +5577,11 @@ const char* Track::GetNameAsUTF8() const
     return m_info.nameAsUTF8;
 }
 
+const char* Track::GetLanguage() const
+{
+    return m_info.language;
+}
+
 const char* Track::GetCodecNameAsUTF8() const
 {
     return m_info.codecNameAsUTF8;
@@ -6607,6 +6619,17 @@ long Tracks::ParseTrackEntry(
             if (status)
                 return status;
         }
+        else if (id == 0x02B59C)  //Track Language
+        {
+            const long status = UnserializeString(
+                                    pReader,
+                                    pos,
+                                    size,
+                                    info.language);
+
+            if (status)
+                return status;
+        }
         else if (id == 0x06)  //CodecID
         {
             const long status = UnserializeString(