sdl2: Initial commit SDL 2.0 from upstream.

Source: http://hg.libsdl.org/SDL
Changeset: 7064 (239ce872e8d4)
sdl2: Move licenses, etc. to subdir, and ensure example never builds.

The android project provided by SDL is an example and not a dependency
of our application.  We rename the make files to ensure that the
example never gets built accidentally.
sdl2: Use GLES2 instead of GLES1.
build: Update makefiles to easily switch between SDL 1.3/2.0.

Build variable SDL_MODULE := {SDL, SDL2} specifies the SDL version to
use.

Added ae-imports to SDL2 dependencies.
build: Build app with SDL2.
Merge branch 'master' into sdl2
bugfix: Hack-fix GL context creation failure on some devices.

My Xperia PLAY (stock 2.3.3) was unable to create the context when the
buffer size was specified.  This is a bandaid fix... don't know how
generally it applies, and don't understand the underlying defect yet.
front: Add some debug logging.
bugfix: Add secondary fallback to gl context creation failure.

If the first fallback doesn't work, then just fall all the way back to
the context specification we had been using with SDL 1.3.
Merge branch 'sdl2'