Add call to update_cvstat() in setup_surfaces()

This should ensure that cvstat has the right window size at the start.
I hope.

src/conio/sdl_con.c

@@ -694,6 +694,7 @@ static void setup_surfaces(struct video_stats *vs)
 	}
 	pthread_mutex_unlock(&win_mutex);
 	vstat.scaling = sdl_getscaling();
+	update_cvstat(vs);
 }
 
 /* Called from event thread only */