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_guid.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
@@ -19,10 +19,13 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 
+/* WIKI CATEGORY: GUID */
+
 /**
- *  \file SDL_guid.h
+ * # CategoryGUID
  *
- *  Include file for handling ::SDL_GUID values.
+ * A GUID is a 128-bit value that represents something that is uniquely
+ * identifiable by this value: "globally unique."
  */
 
 #ifndef SDL_guid_h_
@@ -38,34 +41,38 @@ extern "C" {
 #endif
 
 /**
- * An SDL_GUID is a 128-bit identifier for an input device that
- *   identifies that device across runs of SDL programs on the same
- *   platform.  If the device is detached and then re-attached to a
- *   different port, or if the base system is rebooted, the device
- *   should still report the same GUID.
+ * An SDL_GUID is a 128-bit identifier.
  *
- * GUIDs are as precise as possible but are not guaranteed to
- *   distinguish physically distinct but equivalent devices.  For
- *   example, two game controllers from the same vendor with the same
- *   product ID and revision may have the same GUID.
+ * This is an acronym for "Globally Unique ID."
  *
- * GUIDs may be platform-dependent (i.e., the same device may report
- *   different GUIDs on different operating systems).
+ * While a GUID can be used to assign a unique value to almost anything, in
+ * SDL these are largely used to identify input devices across runs of SDL
+ * programs on the same platform.If the device is detached and then
+ * re-attached to a different port, or if the base system is rebooted, the
+ * device should still report the same GUID.
+ *
+ * GUIDs are as precise as possible but are not guaranteed to distinguish
+ * physically distinct but equivalent devices. For example, two game
+ * controllers from the same vendor with the same product ID and revision may
+ * have the same GUID.
+ *
+ * GUIDs may be platform-dependent (i.e., the same device may report different
+ * GUIDs on different operating systems).
  */
-typedef struct {
+typedef struct SDL_GUID {
     Uint8 data[16];
 } SDL_GUID;
 
 /* Function prototypes */
 
 /**
- * Get an ASCII string representation for a given ::SDL_GUID.
+ * Get an ASCII string representation for a given SDL_GUID.
  *
  * You should supply at least 33 bytes for pszGUID.
  *
- * \param guid the ::SDL_GUID you wish to convert to string
- * \param pszGUID buffer in which to write the ASCII string
- * \param cbGUID the size of pszGUID
+ * \param guid the SDL_GUID you wish to convert to string.
+ * \param pszGUID buffer in which to write the ASCII string.
+ * \param cbGUID the size of pszGUID.
  *
  * \since This function is available since SDL 2.24.0.
  *
@@ -74,14 +81,14 @@ typedef struct {
 extern DECLSPEC void SDLCALL SDL_GUIDToString(SDL_GUID guid, char *pszGUID, int cbGUID);
 
 /**
- * Convert a GUID string into a ::SDL_GUID structure.
+ * Convert a GUID string into a SDL_GUID structure.
  *
  * Performs no error checking. If this function is given a string containing
  * an invalid GUID, the function will silently succeed, but the GUID generated
  * will not be useful.
  *
- * \param pchGUID string containing an ASCII representation of a GUID
- * \returns a ::SDL_GUID structure.
+ * \param pchGUID string containing an ASCII representation of a GUID.
+ * \returns a SDL_GUID structure.
  *
  * \since This function is available since SDL 2.24.0.
  *