Update SDL2 to 2.0.4

code/SDL2/include/SDL_error.h

@@ -1,6 +1,6 @@
 /*
   Simple DirectMedia Layer
-  Copyright (C) 1997-2014 Sam Lantinga <slouken@libsdl.org>
+  Copyright (C) 1997-2016 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
@@ -38,7 +38,7 @@ extern "C" {
 
 /* Public functions */
 /* SDL_SetError() unconditionally returns -1. */
-extern DECLSPEC int SDLCALL SDL_SetError(const char *fmt, ...);
+extern DECLSPEC int SDLCALL SDL_SetError(SDL_PRINTF_FORMAT_STRING const char *fmt, ...) SDL_PRINTF_VARARG_FUNC(1);
 extern DECLSPEC const char *SDLCALL SDL_GetError(void);
 extern DECLSPEC void SDLCALL SDL_ClearError(void);