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_common.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_common.h
  *
  *  Include file for SDL test framework.
@@ -129,7 +129,7 @@ extern "C" {
 
 /* Function prototypes */
 
-/**
+/*
  * \brief Parse command line parameters and create common state.
  *
  * \param argv Array of command line parameters
@@ -139,7 +139,7 @@ extern "C" {
  */
 SDLTest_CommonState *SDLTest_CommonCreateState(char **argv, Uint32 flags);
 
-/**
+/*
  * \brief Process one common argument.
  *
  * \param state The common state describing the test window to create.
@@ -150,7 +150,7 @@ SDLTest_CommonState *SDLTest_CommonCreateState(char **argv, Uint32 flags);
 int SDLTest_CommonArg(SDLTest_CommonState * state, int index);
 
 
-/**
+/*
  * \brief Logs command line usage info.
  *
  * This logs the appropriate command line options for the subsystems in use
@@ -164,7 +164,7 @@ int SDLTest_CommonArg(SDLTest_CommonState * state, int index);
  */
 void SDLTest_CommonLogUsage(SDLTest_CommonState * state, const char *argv0, const char **options);
 
-/**
+/*
  * \brief Returns common usage information
  *
  * You should (probably) be using SDLTest_CommonLogUsage() instead, but this
@@ -177,7 +177,7 @@ void SDLTest_CommonLogUsage(SDLTest_CommonState * state, const char *argv0, cons
  */
 const char *SDLTest_CommonUsage(SDLTest_CommonState * state);
 
-/**
+/*
  * \brief Open test window.
  *
  * \param state The common state describing the test window to create.
@@ -186,7 +186,7 @@ const char *SDLTest_CommonUsage(SDLTest_CommonState * state);
  */
 SDL_bool SDLTest_CommonInit(SDLTest_CommonState * state);
 
-/**
+/*
  * \brief Easy argument handling when test app doesn't need any custom args.
  *
  * \param state The common state describing the test window to create.
@@ -197,7 +197,7 @@ SDL_bool SDLTest_CommonInit(SDLTest_CommonState * state);
  */
 SDL_bool SDLTest_CommonDefaultArgs(SDLTest_CommonState * state, const int argc, char **argv);
 
-/**
+/*
  * \brief Common event handler for test windows.
  *
  * \param state The common state used to create test window.
@@ -207,7 +207,7 @@ SDL_bool SDLTest_CommonDefaultArgs(SDLTest_CommonState * state, const int argc,
  */
 void SDLTest_CommonEvent(SDLTest_CommonState * state, SDL_Event * event, int *done);
 
-/**
+/*
  * \brief Close test window.
  *
  * \param state The common state used to create test window.
@@ -215,7 +215,7 @@ void SDLTest_CommonEvent(SDLTest_CommonState * state, SDL_Event * event, int *do
  */
 void SDLTest_CommonQuit(SDLTest_CommonState * state);
 
-/**
+/*
  * \brief Draws various window information (position, size, etc.) to the renderer.
  *
  * \param renderer The renderer to draw to.