vivante_swizzle | Texture swizzle with supertiling for Vivante chips

vivante_swizzle is a C++ library. vivante_swizzle has no bugs, it has no vulnerabilities and it has low support. However vivante_swizzle has a Non-SPDX License. You can download it from GitHub.

i wrote the post "texture tiling and swizzling" (almost exactly 3 years ago, but i never did a proper example, simply because all the actual implementations of that technique that i'd written up to that point were for hardware i had signed ndas for. well, today i got a question about this relating to the "supertiling" scheme used by vivante chips (as it happens, that scheme matches the model described in the article exactly, is relatively simple, and most importantly, i've never signed any ndas with (or gotten hardware docs from) vivante, so there shouldn't be any legal problems. so here goes: a full implementation of the technique as intended, for a format used by actual existing gpu hardware, plus small test driver. this code is optimized for readability not maximum performance; but i think it