Frank Zago to SDL

For those interested, here's a snapshot of the current port. I did away with
most of the previous attempt which was based of the sprite engine, because the
support is limited to 128 64x64 sprites. Instead I'm using the gl engine.
The drawback is that either the frame buffer or the gl engine can be used
because there's not that much video memory on a DS.

With minimal changes to their code, it can now run the following tests: ,
testspriteminimal, testscale and testsprite2. The last 2 only run under the
emulator for some reason. The tests are not included in this patch for size
reason.

In 16 bits mode, the 16th bit indicated transparency/opacity. If 0, the color
is not displayed. So I had to patch a few core file to set that bit to 1. See
patch for src/video/SDL_RLEaccel.c and src/video/SDL_blit.h. Is that ok, or is
there a better way ?

The nds also doesn't support windowed mode, so I force the fullscreen in
src/video/SDL_video.c.  Is that ok, or is there a better way ?

To get a smaller library, I also tried to not compile the software renderer
when the hardware renderer is compiled in, and define SDL_NO_COMPAT; however
the compilation eventually fails in SDL_surface.c because SDL_SRCCOLORKEY is
defined in SDL_compat.h. Is SDL_NO_COMPAT only for application and not SDL
itself ?