GUI2/Window: removed CVideo getter

One should use CVideo::get_singleton instead since there's only one CVideo object anyway.
This class just has a convenience reference to it.

src/gui/widgets/window.cpp

@@ -683,7 +683,7 @@ void window::draw()
 		assert(!item.empty());
 
 		const SDL_Rect dirty_rect
-				= new_widgets ? video().screen_area()
+				= new_widgets ? video_.screen_area()
 							  : item.back()->get_dirty_rectangle();
 
 // For testing we disable the clipping rect and force the entire screen to

src/gui/widgets/window.hpp

@@ -346,11 +346,6 @@ class window : public panel
 
 	/***** ***** ***** setters / getters for members ***** ****** *****/
 
-	CVideo& video()
-	{
-		return video_;
-	}
-
 	/**
 	 * Sets there return value of the window.
 	 *