Added SDL GL buffer swap

include/Window.h

 
     virtual void writeString(WindowString *s) = 0;
 
+    virtual void swapBuffersGL() = 0;
+
     virtual void resizeGL(unsigned int w, unsigned int h);
 };
 

include/WindowSDL.h

 
     virtual void writeString(WindowString *s);
 
+    virtual void swapBuffersGL();
+
 private:
     bool mInit;
     char *mDriver;

src/WindowSDL.cpp

 
 }
 
+void WindowSDL::swapBuffersGL() {
+    SDL_GL_SwapWindow(mWindow);
+}
+