Added support for OpenGL ES and UIKit Video Driver: - included SDL_renderer_gles.h - added UIKit Video driver bootstrap declaration - added property "retained_backing" to gl_config structure. Having retained backing means your video buffers can't be overwritten by other applications between drawing frames. By default, this is enabled. I wanted to give the option to disable this on iPhone because it increases performance greatly. - modified SDL_GetAttribute and SDL_SetAttribute function for OpenGL ES support. OpenGL ES does not have support for accumulation buffers, and is always double buffered, among other things.

The reason these libraries are built outside of the standard XFree86
tree is so that they can be linked as shared object code directly into
SDL without causing any symbol collisions with code in the application.

You can't link static library code into shared libraries on non-x86
Linux platforms.  Since these libraries haven't become standard yet,
we'll just include them directly.

These sources are synchronized with XFree86 4.2.1