Created attachment 2596 [details]
Remove Haiku specific dynamic object loading and replace it with posix

SDL2 on Haiku so far uses Haiku-specific APIs for loading dynamic objects as add-ons, instead of using dlopen to load them as libraries. This, for example, leads to SDL_mixer not being able to load its audio backends, when compiled with standard settings.

As discussed at https://www.freelists.org/post/haikuports/SDL2-mixer-ogg-music-not-playing-and-other-stuff,2 , the best way to deal with this would be using dlopen instead of load_add_on. The following patch implements this change by dropping the Haiku-specific bits and using dlopen instead.

Note that no change was made to CMakeLists.txt, as that already appears to use dlopen even on Haiku, though I have not tested that specifically.