[new] devel/sdl2_audiolib

Hello,

Here's a new port for a forthcoming update to devilutionX.

SDL_audiolib is an audio decoding, resampling and mixing library.

It is a small and simple to use C++ library for playing various audio
formats. It is a thin (-ish) wrapper around existing resampling (like
SRC or SoX) and decoding libraries (like libmpg123 or libvorbis).

Most popular audio formats are supported.

Thanks to bcallah for the review and updates

Thanks,
Lucas