Update to OpenGL 2.1

[aaspectre]

another lead for the impatient like me may be compiling and installing alyssa rosenzweig's personal fork of mesa (something I tried yesterday, but failed as i was rushing and not really reading the docs(clearly replacing the git url in the mesa-git aur pkgbuild isn't enough!). second of all, her fork will undoubtedly be merged upstream anyway, so this is for the very impatient), as she seems to be the main person responsible for progressing panfrost