Program runs successfully on Linux

The current approach is to create an SDL window without a GL context, and let Ogre3D create its own GL context. Ogre is then instructed to draw to the SDL window instead of creating its own.

If this ever causes problems in the future, the following blog entry shows an approach where SDL creates the GL context and tells Ogre3D to use that instead of its own, as well as the SDL window:
[Setup OGRE3D with SDL2 + CEGUI](http://digiorgi.info/233/setup-ogre3d-with-sdl2-cegui/)