Declare the SetWindowIcon function

src/yuzu_cmd/emu_window/emu_window_sdl2.h

@@ -31,7 +31,10 @@ public:
 
     /// Wait for the next event on the main thread.
     void WaitEvent();
-
+    
+    // Sets the window icon from yuzu.bmp
+	void SetWindowIcon();    
+    
 protected:
     /// Called by WaitEvent when a key is pressed or released.
     void OnKeyEvent(int key, u8 state);