Fix compilation with latest TagLib git master

The latest taglib `RIFF::WAV::File::tag` now returns `TagLib::Tag *`
instead of `ID3v2::Tag *`. The old behaviour was kept only for backwards
compatibility and was slated to be fixed in TagLib 2.0.

The 1:1 replacement is `RIFF::WAV::File::ID3v2Tag`, which was added in
TagLib 1.9 (released 10 years ago).

src/extractors/taglibextractor.cpp

@@ -583,8 +583,8 @@ void TagLibExtractor::extract(ExtractionResult* result)
             extractAudioProperties(&file, result);
             readGenericProperties(file.properties(), result);
             if (file.hasID3v2Tag()) {
-                result->addImageData(extractId3Cover(file.tag(), imageTypes));
-                extractId3Tags(file.tag(), result);
+                result->addImageData(extractId3Cover(file.ID3v2Tag(), imageTypes));
+                extractId3Tags(file.ID3v2Tag(), result);
             }
         }
     } else if (mimeType == QLatin1String("audio/x-musepack")) {

src/writers/taglibwriter.cpp

@@ -555,7 +555,7 @@ void TagLibWriter::write(const WriteData& data)
             auto savedProperties = file.properties();
             writeGenericProperties(savedProperties, properties);
             file.setProperties(savedProperties);
-            auto id3Tags = dynamic_cast<TagLib::ID3v2::Tag*>(file.tag());
+            auto id3Tags = file.ID3v2Tag();
             if (id3Tags) {
                 writeID3v2Tags(id3Tags, properties);
                 writeID3v2Cover(id3Tags, data.imageData());