Update SDL2 to latest source (1a50334)

libs/SDL2/include/SDL_pixels.h

@@ -1,6 +1,6 @@
 /*
   Simple DirectMedia Layer
-  Copyright (C) 1997-2021 Sam Lantinga <slouken@libsdl.org>
+  Copyright (C) 1997-2022 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
@@ -301,6 +301,11 @@ typedef enum
         SDL_DEFINE_PIXELFOURCC('O', 'E', 'S', ' ')
 } SDL_PixelFormatEnum;
 
+/**
+ * The bits of this structure can be directly reinterpreted as an integer-packed
+ * color which uses the SDL_PIXELFORMAT_RGBA32 format (SDL_PIXELFORMAT_ABGR8888
+ * on little-endian systems and SDL_PIXELFORMAT_RGBA8888 on big-endian systems).
+ */
 typedef struct SDL_Color
 {
     Uint8 r;