Backport SDL 2-dependent new input/sound/platform features to Windows 98 about ssg HOT 2 OPEN

Turns out that miniaudio has two disadvantages when it comes to the features needed for #9:

1. It doesn't provide APIs for accessing FLAC or Ogg metadata, even though its vendored libraries have the code for it.
2. Its fader is linear rather than logarithmic, with no way to customize it.

With 1) forcing me to separately include the same libraries anyway, I've moved FLAC/Vorbis decoding and fading to the platform-independent game layer, using an adapted version of thcrap's BGM streaming code. miniaudio now only receives the raw audio stream, which means that we only ended up using it for features that DirectSound also supports.

Thus, it would make slightly more sense to go for 2) in the case of sound. Then, we not only get FLAC/Vorbis BGM modding on Windows 98, but even the modern SDL Windows build could ditch miniaudio and go back to DirectSound, reducing binary size and release build link times.

from ssg.

Option 1 (porting SDL 2 to Windows 98) has received €62.50 in microtransaction funding from M0003.

from ssg.