[SSX 3] GST (PS2 GS texture compression) & 8bpp textures

[modeco80]

Triage issue

[modeco80]

As it turns out, GST isn't a priority, and dev / 1d9edf0 fixes this. Closing upon dev merge to master.

[modeco80]

Or... Not? Some textures in BAM and TEXPS2 use something strange.. Gimex can handle it