Ignore first mouse event

ChangeLog

  OpenRaider (0.1.2) xythobuz <xythobuz@xythobuz.de>
 
 	[ 20140101 ]
+	* Added bool mFirstMouseEvent to SDLSystem used to ignore
+	  the first received mouse event, because its faulty, thanks
+	  to an SDL bug:
+	  http://gamedev.stackexchange.com/questions/33519/trap-mouse-in-sdl#comment56642_33554
 	* Fixed incredibly slow mouse/camera movements
 	* Fixed mouse grabbing in fullscreen mode. Also make mouse
 	  invisible and grab it in windowed mode

src/SDLSystem.cpp

 	mWindow = 0x0;
 	gWidth = &m_width;
 	gHeight = &m_height;
+    mFirstMouseEvent = false;
 }
 
 
 				break;
 			case SDL_MOUSEMOTION:
 				// Wrap motion
-				handleMouseMotionEvent(event.motion.xrel/2, -event.motion.yrel/2);
+                if (!mFirstMouseEvent) {
+                    mFirstMouseEvent = true;
+                } else {
+                    handleMouseMotionEvent(event.motion.xrel/2, event.motion.yrel/2);
+                }
 				break;
 			case SDL_MOUSEBUTTONDOWN:
 			case SDL_MOUSEBUTTONUP:

src/SDLSystem.h

  protected:
     int m_old_width;
     int m_old_height;
+    bool mFirstMouseEvent; // Filter first mouse event (SDL bug)
 
  private: