Introductory patch

Hi,

Here is what I did to make the game run in multi-player under Linux+SDL. Currently, it will not start as there is no action taken when the Pause button is pressed. I saw a flag called Input_SDL::pause that was not being touched, so I figured I'd set it and that did the trick.

I also added a command-line switch to start the game in fullscreen, since I prefer to play it that way.

I plan to make more fixes/improvements in my free time, so hopefully I get more of it in the near future