UFO:Alien Invasion Code

* More music track size-reduction.
* Some tracks are brought down in volume just a little bit to avoid clipping.
* "Defeat Fear" needed a slight amount of editing, the original had a burst of random noise at the end (now removed), and didn't loop well (now fixed with a subtle, quick fade-out). I did my best to keep editing to a minimum.

* new music track by slippycurb (cc-by 3.0)