Implement audio probing to reduce audio false positive.

src/modules/sound/lullaby/VorbisDecoder.cpp

@@ -97,6 +97,19 @@ VorbisDecoder::~VorbisDecoder()
 	ov_clear(&handle);
 }
 
+int VorbisDecoder::probe(Stream *stream)
+{
+	char header[4];
+
+	if (stream->read(header, 4) >= 4)
+	{
+		if (memcmp(header, "OggS", 4) == 0)
+			return 60;
+	}
+
+	return 1;
+}
+
 love::sound::Decoder *VorbisDecoder::clone()
 {
 	StrongRef<Stream> s(stream->clone(), Acquire::NORETAIN);