video: Don't check if we can use a "texture framebuffer" until needed. This prevents SDL from making an OpenGL context and maybe throwing it away immediately by default. It will now only do it when trying to request a window framebuffer directly, or creating an SDL_Renderer with the "software" backend, which makes that request itself. The way SDL decides if it should use a "texture framebuffer" needs dramatic updating, but this solves the immediate problem. Reference Issue #4624.