Build type information on first use (load-time), instead of using a hardcoded list

--HG--
branch : dynamiccore2

src/modules/sound/Decoder.cpp

@@ -27,6 +27,8 @@ namespace love
 namespace sound
 {
 
+love::Type Decoder::type(&Object::type);
+
 Decoder::Decoder(Data *data, const std::string &ext, int bufferSize)
 	: data(data)
 	, ext(ext)