main: preparation for bringing SDL2 back properly

Figured out that using SDL with OpenGL ES 2.0 headers basically restricts you to that, even though SDL will select full OGL on a platform supporting that but will fall back on OGLES2.0. Therefore my little stunt with using X11 directly has not paid off and I'd rather not reinvent the wheel when working with X11. As a matter of fact I'd run as far away from it as possible. SDL2's git already has wayland support so I'll check it out soon enough. I cannot port back to SDL2 right now because it turns out my X is broken. No, no, not running Arch. Debian experimental's X is broken though, so I'll need to figure out a way to go back to unstable one's.