Comments and code formatting.
Game balancing changes.

Change: Vehicles can now only go backwards up to 50% of their maximum
velocity.
Change: Vehicles can inflict damage when moving backwards.
Now playing one of 3 (prev 2) possible sounds on crash.
Updated INSTALL instructions.
Updated comments.
Changes in HISTORY and README files.
Changes in game packaging.

Game no longer placed in /usr/local/games/savagewheels subfolder inside
the tar.gz package.