EMI: Allow the user to skip the intro movie in the EMI Demo.

This change allows the user to skip the intro movie by pressing ESC. It works on the original engine, but not here. I haven't figured out if there's an error in the scripts, but I'm not seeing a way to skip it.

In the actual game, they wrap StartMovie with the Lua function RunFullscreenMovie which handles skipping the movie by setting a new button handler.