The following patch fixes some of the bitrot for the Nintendo DS port.
The support is still basic at the moment, but it allows to run the "general"
test under the current head of tree (parent: 5269:11bd1585efb5 tip).
Most of the patch is mine, but I integrated a couple changes that John
Magnotti posted on Feb 1st.

Prefer the OpenGL ES 2.0 context when it's available, make it possible to create an OpenGL 2.0 context on iPhoneOS

This compiles, but it untested.

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.

This allows me to reduce the set of formats supported by the renderers to the most optimal set, for a nice speed boost.

--HG--
rename : src/video/SDL_yuv_mmx.c => src/render/SDL_yuv_mmx.c
rename : src/video/SDL_yuv_sw.c => src/render/SDL_yuv_sw.c
rename : src/video/SDL_yuv_sw_c.h => src/render/SDL_yuv_sw_c.h
rename : src/video/mmx.h => src/render/mmx.h

Moved the rendering code out to a separate directory in the hope that it can someday be completely decoupled from the rest of the library and be expanded to an awesome 2D on 3D library.

--HG--
rename : src/video/windows/SDL_d3drender.c => src/render/direct3d/SDL_d3drender.c
rename : src/video/SDL_renderer_gl.c => src/render/opengl/SDL_renderer_gl.c
rename : src/video/SDL_renderer_gles.c => src/render/opengles/SDL_renderer_gles.c
rename : src/video/SDL_renderer_sw.c => src/render/software/SDL_renderer_sw.c