Update SDL to version 2.0.10.

libs/SDL2/include/SDL_events.h

@@ -1,6 +1,6 @@
 /*
   Simple DirectMedia Layer
-  Copyright (C) 1997-2018 Sam Lantinga <slouken@libsdl.org>
+  Copyright (C) 1997-2019 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
@@ -594,6 +594,9 @@ typedef union SDL_Event
     Uint8 padding[56];
 } SDL_Event;
 
+/* Make sure we haven't broken binary compatibility */
+SDL_COMPILE_TIME_ASSERT(SDL_Event, sizeof(SDL_Event) == 56);
+
 
 /* Function prototypes */