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_test_crc32.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
@@ -19,7 +19,7 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 
-/**
+/*
  *  \file SDL_test_crc32.h
  *
  *  Include file for SDL test framework.
@@ -60,7 +60,7 @@ extern "C" {
  #define CRC32_POLY 0xEDB88320   /* Perl String::CRC32 compatible */
 #endif
 
-/**
+/*
  * Data structure for CRC32 (checksum) computation
  */
   typedef struct {
@@ -69,7 +69,7 @@ extern "C" {
 
 /* ---------- Function Prototypes ------------- */
 
-/**
+/*
  * \brief Initialize the CRC context
  *
  * Note: The function initializes the crc table required for all crc calculations.
@@ -82,7 +82,7 @@ extern "C" {
  int SDLTest_Crc32Init(SDLTest_Crc32Context * crcContext);
 
 
-/**
+/*
  * \brief calculate a crc32 from a data block
  *
  * \param crcContext         pointer to context variable
@@ -101,7 +101,7 @@ int SDLTest_Crc32CalcEnd(SDLTest_Crc32Context * crcContext, CrcUint32 *crc32);
 int SDLTest_Crc32CalcBuffer(SDLTest_Crc32Context * crcContext, CrcUint8 *inBuf, CrcUint32 inLen, CrcUint32 *crc32);
 
 
-/**
+/*
  * \brief clean up CRC context
  *
  * \param crcContext        pointer to context variable