sdl12-compat: Patched to compile against older SDL2 headers.

SDL Commits
1 
From 995af0f1dc5cbf7a822d2640c8def0b04dfd22f8 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Wed, 29 Nov 2023 13:23:26 -0500
Subject: [PATCH] Patched to compile against older SDL2 headers.

(Headers up to the 2.0.9 release need this.)

Fixes #324.
---
 src/SDL20_include_wrapper.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/SDL20_include_wrapper.h b/src/SDL20_include_wrapper.h
index 785b89e47..083dc5ea6 100644
--- a/src/SDL20_include_wrapper.h
+++ b/src/SDL20_include_wrapper.h
@@ -921,6 +921,12 @@
 #error You need to compile against SDL >= 2.0.7 headers.
 #endif
 
+#if !SDL_VERSION_ATLEAST(2,0,10)
+// SDL_PixelFormatEnum was an anonymous enum before SDL 2.0.10.
+// Force it to Uint32 if compiling on older headers.
+typedef Uint32 SDL_PixelFormatEnum;
+#endif
+
 /* Missing SDL_thread.h stuff (see above) */
 #if defined(_WIN32) || defined(__OS2__)
 typedef struct SDL_Thread SDL_Thread;