New input mode: "Side buttons". Shows left and right steering buttons in the bottom corners of the screen and a trigger bonus button in the middle right of the screen. Hold left and right simultaneously to go backward.

Tiny-sur-mer: plugged several holes and added missing fences.

Adjusted the probabilities of bonuses so all bonuses have a chance to be picked. You still have more chance to get a mine than a gun or missile when your rank is high.

Other bug fixes (see changelog).
