along with options to select backends for windowing, rendering, audio and controls in the Makefile
use RENDER_API=D3D11 or D3D12 for the D3D renderers, that will also automatically enable using DXGI for windowing; SDL2 will still be used for input and audio for the time being
also adds three-point filtering to the OpenGL backend and an option for it in the menu
uses two different methods, with the first one taking priority if it's available:
a) use the fog factor supplied in the fog colors as a GL_FOG_COORD; GL_FOG_COORD is only available in GL1.4+ or when GL_EXT_fog_coord is present
just blend the same triangles a second time, but replace the color with fog color and multiply the alpha by fog alpha
fgsfds