Got rid of SDL

	* Since I will probably never implement
	  an SDL GUI (I know SDL and want to play
	  with ncurses, so I'll probably do an
	  ncurses GUI someday), let's remove SDL
	  dependencies. The only ones were SDL_Thread
	  and SDL_Timers. SDL_Thread was replaced by
	  pthread. I'll end up reimplementing
	  the SDL_Timer code with a pthread for my
	  very simple need.

Signed-off-by: sebhz <seb@zyglute.fr>