Replace signals with Q_SIGNALS

src/musicbrainz/acoustidclient.h

@@ -60,7 +60,7 @@ class AcoustidClient : public QObject {
   // Cancels all requests.  Finished() will never be emitted for any pending requests.
   void CancelAll();
 
- signals:
+ Q_SIGNALS:
   void Finished(const int id, const QStringList &mbid_list, const QString &error = QString());
 
  private slots:

src/musicbrainz/musicbrainzclient.h

@@ -101,7 +101,7 @@ class MusicBrainzClient : public QObject {
   // Cancels all requests.  Finished() will never be emitted for any pending requests.
   void CancelAll();
 
- signals:
+ Q_SIGNALS:
   // Finished signal emitted when fechting songs tags
   void Finished(const int id, const MusicBrainzClient::ResultList &result, const QString &error = QString());
   // Finished signal emitted when fechting album's songs tags using DiscId

src/musicbrainz/tagfetcher.h

@@ -49,7 +49,7 @@ class TagFetcher : public QObject {
  public slots:
   void Cancel();
 
- signals:
+ Q_SIGNALS:
   void Progress(const Song &original_song, const QString &stage);
   void ResultAvailable(const Song &original_song, const SongList &songs_guessed, const QString &error = QString());