Added (experimental) support for a GNU/Linux version of Snes9x (and now Mednafen)

Added very basic GNU/Linux support and added a sample Snes9x emulator which works perfectly on my system.
Please note that I've only tested it on my system, but it did work with both Super Mario Kart and Super Mario World. Ice automatically added launchers and grid images to Steam and I was able to launch the games just fine through Steam.

The GNU/Linux support can still be worked on, but this is a start.