Added support for intro sound configuration

Added intro_sound to sh_options and changed cl_kernel to reflect the
changes.
intro_sound reflects the configuration available for intro_image and
menu_music
Reduced line count.

Fixed push from Chessnut's commit, with the proper copyright info.
https://github.com/Chessnut/Clockwork/commit/2c86d0327072678f49555bf80132ea42d7b9a099
Merge pull request #125 from ametrocavich/master

Added support for intro sound configuration.