This gets the GL and GLSL renderers working for the -win targets... sort of: they are upside down and GLSL's bsp surfaces are black (same as Vulkan). However, with this, all 5 renderers at least limp along for -win, 4/5 work for -sdl.
They're now an enum, and the flag part of the name is all lowercase, but now the flag definitions and names list will never get out of sync.
This includes -win clients (no clue if anything actually works yet).