SDL adds expanded support for the new Steam Controller without Steam

A future release of SDL (Simple DirectMedia Layer) will come with improved support for Valve's new Steam Controller to run without Steam needed. ICYMI: see my original review of the new Steam Controller.

What is SDL? It's a cross-platform development library designed to provide low level access to audio, keyboard, mouse, joystick, and graphics hardware. It's used by various games, game engines and more.

There was already some support in SDL for the new Steam Controller, the latest merged code just expands it. As confirmed in the comments from people testing, it does indeed work without the need of Steam running too. Just before it was merged in the developer responsible for the code noted:

@slouken Okay, I tested with a new Steam Controller and the changes made by this PR work fine. Using testcontroller, the touchpads (click, touch, x, y, pressure), capacitive touch for sticks, and grip sense are all functional. The mapping has been removed for now, though, so of those features, only partial touchpad support remains (touch, x, y, and pressure). The features that were already present prior to this PR are fine too (back buttons, gyro/accel, and QAM button).

What's not addressed by this PR, because it's a separate topic, is the long running problem of Steam Input interfering in various ways. See here for details: #15471 (comment)

Hopefully at some point they'll also be able to solve the issues with Steam Input interfering with SDL too.

Eventually, once a new release of SDL rolls out with this code, we should see nicer Steam Controller support across various games that either use SDL directly or those that just pull gamepad support from it.