Remove CD music as an option in setup tool.

This no longer works since the last commit.
libtextscreen: Convert video code to SDL2.

This gets the basic libtextscreen up and running under SDL2. Not
everything works yet (most notably keyboard input is kind of broken)
but it's a start.
Update library names to SDL2 versions.

Use SDL2_mixer and SDL2_net rather than SDL_mixer/SDL_net.
Update joystick code to use SDL2 API.

SDL_JoystickName() API changed to take a SDL_Joystick handle instead
of an index.
Update video-hr code to SDL2 API.
Disable OS X error dialog box for now.

This doesn't seem to be working.
Update video code to use SDL2 API.

Not everything works correctly yet (keyboard input, among other
things). Remove screen_bpp variable as the new SDL API doesn't seem
to allow us to set this.