Extend GLSurfaceView to make it easy to create an OpenGL ES 2.0 context

Provide a new method, GLSurfaceView.setEGLContextClientVersion. Clients
call this method to define which level of OpenGL ES support they want.

This method only affects the default behavior of GLSurfaceView. If clients
have supplied their own EGLContextFactory or EGLConfigChooser then they
are on their own if they want to create an OpenGL ES 2.0 context.

This API is currently hidden.

Update the gl2_java test to use this new API.

Update the gl2_java test's AndroidManifest.xml file to indicate that
it requires OpenGL ES 2.0.