Mesa Preparing Software Fallback For S3TC Texture Compression

Mesa recently landed BPTC software fallback handling that is a requirement for OpenGL 4.2 support but BPTC is not natively supported by all GPU hardware, particularly on the embedded side. That software emulation support for BPTC is similar to what already has existed within Mesa for the ASTC and ETC formats too. A merge request is pending that also adds S3TC software fallback handling, which helps out some of the smaller, embedded GPU drivers too for getting more games running that are dependent on S3 Texture Compression...