This replaces SDL_mixer with an internal streaming and mixing system,
relying only on basic SDL audio support. It's also a partial refactor of
the audio API, most notably BGM-related. The BGM metadata resource type
is gone, as well as the `.bgm` files. The metadata is now stored inside
the `.opus` files directly, using standard Opus tags.
- RESF_UNSAFE is removed.
- Resources that don't have to be finalized on the main thread can load
completely asynchronously.
- A thread waiting for a concurrent task to complete can start executing
that task itself if it hasn't started yet.
- Refactor the resource loading interface, add support for load-time
dependencies.
- Main-thread finalization of asynchronously loaded resources is now
spread out across multiple frames to mitigate frametime spikes.
- Remove some archaisms from the resource management code.
- Fix potential hashtable synchronization issue.
- Fix some deadlock edge cases.
- Don't spawn more worker threads than there are CPU cores (degrades
performance).
- Add TAISEI_AGGRESSIVE_PRELOAD env variable to attempt to aggressively
discover and preload every possible resource.
- Make r_texture_fill{,_region} expect optimal pixmaps, so that it's
never forced to convert them on the main thread. The optimal format may
be queried with the new r_texture_optimal_pixmap_format_for_type API.
These functions will also no longer needlessly copy the entire image
into a staging buffer - previously they did this even if no conversion
was needed.
- Other random changes to facilitate the stuff above.
The overall effect is somewhat faster load times.
Of course it's still all terrible and full of lock contention because I
suck at concurrent programming, but it's not worse than it was.
Probably.
Fixed all warnings and compile errors.
Confirmed successful compilation without warnings for linux (gcc,
clang), windows (gcc-mingw), osx (clang-osxcross).
