* Preparation for initial Flatpack and FlatHub integration
This integrate some initial changes required for Flatpack and distribution from FlatHub.
Also added some resources that will be used for packaging on Linux.
* Address gdkchan comment
* audio: Implement a SDL2 backend
This adds support to SDL2 as an audio backend.
It has the same compatibility level as OpenAL without its issues.
I also took the liberty of restructuring the SDL2 code to have one
shared project between audio and input.
The configuration version was also incremented.
* Address gdkchan's comments
* Fix update logic
* Add an heuristic to pick the correct target sample count wanted by the game
* Address gdkchan's comments
* Address Ac_k's comments
* Fix audren output
* Address gdkchan's comments
