Update SDL to version 2.0.14.

libs/SDL2/src/SDL_dataqueue.c

@@ -1,6 +1,6 @@
 /*
   Simple DirectMedia Layer
-  Copyright (C) 1997-2019 Sam Lantinga <slouken@libsdl.org>
+  Copyright (C) 1997-2020 Sam Lantinga <slouken@libsdl.org>
 
   This software is provided 'as-is', without any express or implied
   warranty.  In no event will the authors be held liable for any damages
@@ -18,11 +18,10 @@
      misrepresented as being the original software.
   3. This notice may not be removed or altered from any source distribution.
 */
-
 #include "./SDL_internal.h"
+
 #include "SDL.h"
 #include "./SDL_dataqueue.h"
-#include "SDL_assert.h"
 
 typedef struct SDL_DataQueuePacket
 {