Update SDL2 to newest version to fix 7.1 playback

This fixes 7.1 playback. Before this commit, SDL used 7.1 front audio configuration with Center Left and Center Right speakers, but without Rear speakers.

See https://github.com/libsdl-org/SDL/issues/11709 for more details.

libs/SDL2/include/SDL_platform.h

@@ -1,6 +1,6 @@
 /*
   Simple DirectMedia Layer
-  Copyright (C) 1997-2023 Sam Lantinga <slouken@libsdl.org>
+  Copyright (C) 1997-2024 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
@@ -20,9 +20,9 @@
 */
 
 /**
- *  \file SDL_platform.h
+ * # CategoryPlatform
  *
- *  Try to get a standard set of platform defines.
+ * Try to get a standard set of platform defines.
  */
 
 #ifndef SDL_platform_h_
@@ -73,7 +73,13 @@
 #if defined(__APPLE__)
 /* lets us know what version of Mac OS X we're compiling on */
 #include <AvailabilityMacros.h>
+#ifndef __has_extension /* Older compilers don't support this */
+#define __has_extension(x) 0
 #include <TargetConditionals.h>
+#undef __has_extension
+#else
+#include <TargetConditionals.h>
+#endif
 
 /* Fix building with older SDKs that don't define these
    See this for more information:
@@ -166,6 +172,12 @@
 #define WINAPI_FAMILY_WINRT 0
 #endif /* HAVE_WINAPIFAMILY_H */
 
+#if (HAVE_WINAPIFAMILY_H) && defined(WINAPI_FAMILY_PHONE_APP)
+#define SDL_WINAPI_FAMILY_PHONE (WINAPI_FAMILY == WINAPI_FAMILY_PHONE_APP)
+#else
+#define SDL_WINAPI_FAMILY_PHONE 0
+#endif
+
 #if WINAPI_FAMILY_WINRT
 #undef __WINRT__
 #define __WINRT__ 1
@@ -193,8 +205,10 @@
 #undef __GDK__
 #define __GDK__ 1
 #endif
-#if defined(__PSP__)
+#if defined(__PSP__) || defined(__psp__)
+#ifdef __PSP__
 #undef __PSP__
+#endif
 #define __PSP__ 1
 #endif
 #if defined(PS2)