Updated the DirectFB support, from Couriersud

attached is a working directfb driver diff which works with the current
changes. There are a number of changes around it as well, e.g.
configure.in.

The directfb renderdriver right now still depends on a some "includes"
from src/video/directfb. That's why it is not yet moved to the new
render folder.

src/render/SDL_render.c

@@ -52,6 +52,9 @@ static const SDL_RenderDriver *render_drivers[] = {
 #endif
 #if SDL_VIDEO_RENDER_OGL_ES
     &GL_ES_RenderDriver,
+#endif
+#if SDL_VIDEO_RENDER_DIRECTFB
+    &DirectFB_RenderDriver,
 #endif
     &SW_RenderDriver
 };