Changelog:
- SDL2 was updated to lastest master
- DInput was disabled from build configuration (Close#2238)
- HIDAPI was forced enabled on Linux and libusb library name was fixed (Close#2226)
NOTE about HIDAPI support on Linux:
Make sure that your gamepad is accesible to your user for it to be detected by HIDAPI. This can be done via a udev rule like:
```
KERNEL=="hidraw*", MODE="0660", TAG+="uaccess"
```
**NOTE: This rule is given as an example, this can present a security
risk. Make sure to filter by vendor and product ids.**
* 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
