Add OpenAL-Soft 1.15.1 libs for Windows and Mac

This commit adds OpenAL-Soft 1.15.1 reference libraries for Windows and Mac to be included within build archives (to replace Creative's ancient dll.) These libraries match the current OpenAL headers in the source tree.

ioquake3 will use these by default but will fall back to using the older libraries if not present.

Windows files are named in a manner similar to the SDL2 libs (where 32-bit and 64-bit libs can co-exist in the same directory)