Make the global twindow object globally available.

Note: This is a quick an not really elegant change. I'll fix this as
soon as I'll have figured how CVideo and twindow should relate to
eachother.

src/video.cpp

@@ -551,6 +551,12 @@ void CVideo::set_window_icon(surface& icon)
 	assert(window);
 	window->set_icon(icon);
 }
+
+sdl::twindow *CVideo::get_window()
+{
+	return window;
+}
+
 #endif
 
 #if SDL_VERSION_ATLEAST(2, 0, 0)

src/video.hpp

@@ -20,6 +20,10 @@
 
 #include <boost/utility.hpp>
 
+#if SDL_VERSION_ATLEAST(2,0,0)
+#include "sdl/window.hpp"
+#endif
+
 struct surface;
 
 //possible flags when setting video modes
@@ -143,6 +147,8 @@ class CVideo : private boost::noncopyable {
 	 * @param icon                The new icon for the window.
 	 */
 	static void set_window_icon(surface& icon);
+
+	static sdl::twindow *get_window();
 #endif
 
 	/**