Ported to SDL2

-Rendering is done using renderers
-Rendering uses SDL_Texture
-The SDL_Textures are generated from the old SDL_Surfaces
-Text is only drawn when the text or number to draw has changed.
-If anything fails during init, the game will quit.
-Fullscreen mode is not yet supported ( possible SDL error )

Otherwise everything runs smoothly at at up to 1 000 FPS