Log Message:
SDL2: update to 2.0.20

   This is largely a bugfix release, with the following changes:

   General:

     * SDL_RenderGeometryRaw() takes a pointer to SDL_Color, not int. You can
       cast color data in SDL_PIXELFORMAT_RGBA32 format
       (SDL_PIXELFORMAT_ABGR8888 on little endian systems) for this
       parameter.
     * Improved accuracy of horizontal and vertical line drawing when using
       OpenGL or OpenGLES
     * Added the hint SDL_HINT_RENDER_LINE_METHOD to control the method of
       line drawing used, to select speed, correctness, and compatibility.

   Linux:

     * Fixed hotplug controller detection, broken in 2.0.18