sdl2: add upstream patch to fix DirectFB renderer handling

The configure script enables the DirectFB video driver, but forgets to
enable the renderer driver, causing SDL_CreateRenderer() to fail. Add an upstream patch to fix this.

[Peter: reword/extend commit text,
	add git formatted patch from https://github.com/spurious/SDL-mirror

]
Signed-off-by: Peter Thompson <peter.macleod.thompson@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>