Get a list of music decoders that this build of SDL_mixer provides.
Returns number of music decoders available.
This list can change between builds AND runs of the program, if external libraries that add functionality become available. You must successfully call Mix_OpenAudio() or Mix_OpenAudioDevice() before calling this function, as decoders are activated at device open time.
Appearing in this list doesn't promise your specific audio file will decode...but it's handy to know if you have, say, a functioning Ogg Vorbis install.
These return values are static, read-only data; do not modify or free it. The pointers remain valid until you call Mix_CloseAudio().
This function is available since SDL_mixer 2.0.0.